Tag: IP

Technical Details

Published 2010/07/08 by Daoyuan Li

We define a BPF filter as “icmp and dst host <bouncer_ip>”, which filters out all none-ICMP packets and packets not destined to the bouncer. The we compile this filter and set the filter to the capture device.

When the capture device captures a packet, a process_pkt function is called to process the packet. And that is where we validate the packets and then, if the packet is valid, update
the packet and then send it out, or write the packet to a dump file.

The process of validating the packets are as follows:

Validate checksum of IP header.
Validate TTL of IP.
Validate IP source address
Validate ICMP header checksum.
Validate ICMP type and code.

Since we write the packet to a dump file in a separate function, so a pointer to the dump file handler is passed to the processing function when the process_pkt function is called. The same method is used to pass server IP address and test mode flag.

We keep a linked list of all the ICMP echo requests. When a ICMP echo reply is received, we go through the linked list to find out where
the original echo request comes from.

The code is as follows.

bouncer.h:

/* Global definitions for the port bouncer
 * Packet headers and so on
 */

#define _BSD_SOURCE 1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>

/* PCAP declarations*/
#include <pcap.h>

/* Standard networking declaration */
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

/*
 * The following system include files should provide you with the 
 * necessary declarations for Ethernet, IP, and TCP headers
 */

#include <net/if.h>
#include <netinet/if_ether.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>

/* Add any otherdeclarations you may need here... */

#define MAX_PACKET_SIZE 65535

/* Ethernet addresses are 6 bytes */
//#define ETHER_ADDR_LEN	6

/* Ethernet header */
struct sniff_ethernet {
    u_char ether_dhost[ETHER_ADDR_LEN]; /* Destination host address */
    u_char ether_shost[ETHER_ADDR_LEN]; /* Source host address */
    u_short ether_type; /* IP? ARP? RARP? etc */
};

/* IP header */
struct sniff_ip {
    u_char ip_vhl; /*version << 4 | header length >> 2 */
    u_char ip_tos; /* type of service */
    u_short ip_len; /* total length */
    u_short ip_id; /* identification */
    u_short ip_off; /* fragment offset field */
#define IP_RF 0x8000		/* reserved fragment flag */
#define IP_DF 0x4000		/* dont fragment flag */
#define IP_MF 0x2000		/* more fragments flag */
#define IP_OFFMASK 0x1fff	/* mask for fragmenting bits */
    u_char ip_ttl; /*time to live */
    u_char ip_p; /* protocol */
    u_short ip_sum; /* checksum */
    struct in_addr ip_src, ip_dst; /* source and dest address */
};
#define IP_HL(ip)		(((ip)->ip_vhl) & 0x0f)
#define IP_V(ip)		(((ip)->ip_vhl) >> 4)

/* ICMP header */
struct sniff_icmp {
    u_char icmp_type;
#define ICMP_ECHO 0x8
#define ICMP_REPLY 0x0
    u_char icmp_code;
    u_int16_t icmp_sum;
    u_int16_t icmp_id;
u_int16_t icmp_sequence;
};

#define SIZE_ETHERNET 14
#define SIZE_ICMP 8

#define IP_QUAD(ip)  (ip)>>24,((ip)&0x00ff0000)>>16,((ip)&0x0000ff00)>>8,((ip)&0x000000ff)

struct request{
    struct request* next;
    struct sniff_ip* ip;
    struct sniff_icmp* icmp;
};

/* Global definitions for the port bouncer

* Packet headers and so on

#define _BSD_SOURCE 1

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <errno.h>

#include <unistd.h>

/* PCAP declarations*/

#include <pcap.h>

/* Standard networking declaration */

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

* The following system include files should provide you with the

* necessary declarations for Ethernet, IP, and TCP headers

#include <net/if.h>

#include <netinet/if_ether.h>

#include <netinet/ip.h>

#include <netinet/tcp.h>

/* Add any otherdeclarations you may need here... */

#define MAX_PACKET_SIZE 65535

/* Ethernet addresses are 6 bytes */

//#define ETHER_ADDR_LEN 6

/* Ethernet header */

struct sniff_ethernet {

u_char ether_dhost[ETHER_ADDR_LEN]; /* Destination host address */

u_char ether_shost[ETHER_ADDR_LEN]; /* Source host address */

u_short ether_type; /* IP? ARP? RARP? etc */

};

/* IP header */

struct sniff_ip {

u_char ip_vhl; /*version << 4 | header length >> 2 */

u_char ip_tos; /* type of service */

u_short ip_len; /* total length */

u_short ip_id; /* identification */

u_short ip_off; /* fragment offset field */

#define IP_RF 0x8000 /* reserved fragment flag */

#define IP_DF 0x4000 /* dont fragment flag */

#define IP_MF 0x2000 /* more fragments flag */

#define IP_OFFMASK 0x1fff /* mask for fragmenting bits */

u_char ip_ttl; /*time to live */

u_char ip_p; /* protocol */

u_short ip_sum; /* checksum */

struct in_addr ip_src, ip_dst; /* source and dest address */

};

#define IP_HL(ip) (((ip)->ip_vhl) & 0x0f)

#define IP_V(ip) (((ip)->ip_vhl) >> 4)

/* ICMP header */

struct sniff_icmp {

u_char icmp_type;

#define ICMP_ECHO 0x8

#define ICMP_REPLY 0x0

u_char icmp_code;

u_int16_t icmp_sum;

u_int16_t icmp_id;

u_int16_t icmp_sequence;

};

#define SIZE_ETHERNET 14

#define SIZE_ICMP 8

#define IP_QUAD(ip) (ip)>>24,((ip)&0x00ff0000)>>16,((ip)&0x0000ff00)>>8,((ip)&0x000000ff)

struct request{

struct request* next;

struct sniff_ip* ip;

struct sniff_icmp* icmp;

};

process_pkt.c:

#include "bouncer.h"

/* CRC
 * Adopted from <a href="http://www.netfor2.com/ipsum.htm">http://www.netfor2.com/ipsum.htm</a>
 */
typedef unsigned short u16;
typedef unsigned long u32;

u16 ip_sum_calc(u16 len_ip_header, u16 buff[]) {
    u16 word16;
    u32 sum =0;
    u16 i;

    // make 16 bit words out of every two adjacent 8 bit words in the packet
    // and add them up
    for (i = 0; i < len_ip_header; i = i + 2) {
        word16 = ((buff[i] << 8)&0xFF00)+(buff[i + 1]&0xFF);
        sum = sum + (u32) word16;
    }

    // take only 16 bits out of the 32 bit sum and add up the carries
    while (sum >> 16)
        sum = (sum & 0xFFFF)+(sum >> 16);

    // one'scomplement the result
    sum = ~sum;

    return ((u16) sum);
}

void process_pkt(u_char *args, struct pcap_pkthdr *header,
        u_char *packet) {
    if(header->caplen < header->len){
        fprintf(stderr, "ERROR: Packet data not captured completely\n");
        return;
    }
    /* Main function to perform the bouncing */
    u_char testmode = *args;
    char *serv_addr = (char *) (args + 1);
    u_int32_t dst_addr =inet_addr(serv_addr);
    //pcap_dumper_t *dumper = NULL;
    u_char *dumper = NULL;
    memcpy(&dumper, args + 2 + strlen(serv_addr), sizeof (pcap_dumper_t *));
    struct request ** prequests = NULL;
    memcpy(&prequests, args + 2 + strlen(serv_addr) + sizeof (pcap_dumper_t *), sizeof (struct request**));
    //struct request *requests = *prequests;

    /* Typecasting packet*/
    struct sniff_ethernet *ethernet; /* The ethernet header */
struct sniff_ip *ip; /* The IP header */
    struct sniff_icmp *icmp; /* The ICMP header */
    char *padding; /* Packet padding */
    u_int size_ip;
    ethernet = (struct sniff_ethernet*) (packet);
    ip = (struct sniff_ip*) (packet + SIZE_ETHERNET);
    size_ip = IP_HL(ip)*4;
    u_int32_t srcip = ntohl(ip->ip_src.s_addr);
    if (size_ip < 20 || size_ip > header->len - SIZE_ETHERNET) {
        fprintf(stderr, "ERROR: Invalid IP header length: %ubytes\n", size_ip);
        if (testmode == 1) {
            header->caplen = 0;
            header->len = 0;
            pcap_dump(dumper, header, packet);
        }
        return;
    }
    icmp = (struct sniff_icmp*) (packet + SIZE_ETHERNET + size_ip);
    padding = (u_char *) (packet + SIZE_ETHERNET + size_ip + SIZE_ICMP);

    /* Validate the packet */
    /* Validate IP header */
    /* Check IP version */
    u_char v = ip->ip_vhl>> 4;
    if(v != 4){
        fprintf(stderr, "ERROR: Wrong IP verison %d\n", v);
        return;
    }
    /* Validate CRC */
    u16 ipbuf[size_ip];
    u16 ipsum = ntohs(ip->ip_sum);
    int i;
    for (i = 0; i < size_ip; i++) {
        if (i == 10 || i == 11)
            ipbuf[i] = 0x00;
        else
            ipbuf[i] = *((u_char *) (packet + SIZE_ETHERNET + i));
    }
    if (ipsum != ip_sum_calc(size_ip, ipbuf)) {
fprintf(stderr, "ERROR: ip checksum mismatch. Dropping packet from %u.%u.%u.%u\n",
                IP_QUAD(srcip));
        if (testmode == 1) {
            header->caplen = 0;
            header->len = 0;
            pcap_dump(dumper, header, packet);
        }
        return;
    }
    /* Validate TTL */
    if (ip->ip_ttl <= 0) {
        fprintf(stderr, "ERROR: ip TTL expired. Dropping packet from %u.%u.%u.%u\n",
IP_QUAD(srcip));
        if (testmode == 1) {
            header->caplen = 0;
            header->len = 0;
            pcap_dump(dumper, header, packet);
        }
        return;
    }
    /* Validate IP source address */
    if (srcip == 0x00000000 || srcip >= 0xE0000000
            || (srcip & 0x000000FF) == 0x000000FF || (srcip & 0x000000FF) == 0x00000000) {
        fprintf(stderr, "ERROR: ip source address invalid. Dropping packetfrom %u.%u.%u.%u\n",
                IP_QUAD(srcip));
        if (testmode == 1) {
            header->caplen = 0;
            header->len = 0;
            pcap_dump(dumper, header, packet);
        }
        return;
    }

    /* Validate ICMP header */
    /* Validate ICMP type and code */
    if (!(icmp->icmp_code == 0 && (icmp->icmp_type == 0 || icmp->icmp_type == 8))) {
        fprintf(stderr, "ERROR: icmp type orcode unsupported. Dropping packet from %u.%u.%u.%u\n",
                IP_QUAD(srcip));
        if (testmode == 1) {
            header->caplen = 0;
            header->len = 0;
            pcap_dump(dumper, header, packet);
        }
        return;
    }
    /* Validate CRC */
    int plen = header->len - SIZE_ETHERNET - size_ip - 8;
    u16 icmpbuf[8 + plen];
    u16 icmpsum = ntohs(icmp->icmp_sum);
    for (i = 0; i < 8;i++) {
        if (i == 2 || i == 3)
            icmpbuf[i] = 0x00;
        else
            icmpbuf[i] = *((u_char *) (packet + SIZE_ETHERNET + size_ip + i));
    }
    for (i = 0; i < plen; i++) {
        icmpbuf[i + 8] = *((u_char *) (padding + i));
    }
    if (icmpsum != ip_sum_calc(8 + plen, icmpbuf)) {
        fprintf(stderr, "ERROR: icmp checksum mismatch. Dropping packet from %u.%u.%u.%u\n",
                IP_QUAD(srcip));
        if(testmode == 1) {
            header->caplen = 0;
            header->len = 0;
            pcap_dump(dumper, header, packet);
        }
        return;
    }

    /* Update the packet */
    if (icmp->icmp_type == 0) {
        /* ICMP echo reply */
        ip->ip_src.s_addr = ip->ip_dst.s_addr;
        /* Search the linked list for client address */
        if (*prequests == NULL) {
            fprintf(stderr, "ERROR: process_pkt: nullrequest linked list\n");
            return;
        } else {
            /* Find where the request comes from */
            struct request *r;
            for (r = *prequests; r != NULL; r = r->next) {
                if (r->icmp->icmp_id == icmp->icmp_id && r->icmp->icmp_sequence == icmp->icmp_sequence) {
                    ip->ip_dst.s_addr = r->ip->ip_src.s_addr;
                    break;
                }
}
            if (r == NULL) {
                fprintf(stderr, "ERROR: no match echo requests in stack\n");
                return;
            }
            /* Remove the request from the linked list */
            struct request *rr = *prequests;
            if (rr == r) {
                free(rr->icmp);
                free(rr->ip);
                *prequests = r->next;
                free(r);
            } else {
                while (rr!= r)
                    rr = rr->next;
                free(rr->icmp);
                free(rr->ip);
                rr->next = r->next;
                free(r);
            }
        }
    } else {
        /* ICMP echo request */
        /* Add new request to linked list */
        struct request *r;
        r = malloc(sizeof (struct request));
        if (r == NULL) {
            perror("ERROR: process_pkt:malloc");
            return;
        }
        struct sniff_ip *ipt = malloc(sizeof (struct sniff_ip));
        if (ipt == NULL) {
            perror("ERROR: process_pkt: malloc");
            return;
        }
        memcpy(ipt, ip, sizeof (struct sniff_ip));
        r->ip = ipt;
        struct sniff_icmp* icmpt = malloc(sizeof (struct sniff_icmp));
        if (icmpt == NULL) {
            perror("ERROR: process_pkt: malloc");
return;
        }
        memcpy(icmpt, icmp, sizeof (struct sniff_icmp));
        r->icmp = icmpt;
        r->next = *prequests;
        *prequests = r;
        /* Update destination address */
        ip->ip_src.s_addr = ip->ip_dst.s_addr;
        ip->ip_dst.s_addr = dst_addr;
    }
    /* Recaculate CRC */
    for (i = 0; i < size_ip; i++) {
        if (i == 10 || i == 11)
            ipbuf[i] = 0x00;
        else
ipbuf[i] = *((u_char *) (packet + SIZE_ETHERNET + i));
    }
    ip->ip_sum = htons(ip_sum_calc(size_ip, ipbuf));
    if (testmode == 0) {
        pcap_t *handle = NULL;
        char errbuf[PCAP_ERRBUF_SIZE], *device = "tap0";
        memset(errbuf, 0, PCAP_ERRBUF_SIZE);
        if ((handle = pcap_open_live(device, MAX_PACKET_SIZE, 1, 512, errbuf)) == NULL) {
            fprintf(stderr, "ERROR: %s\n", errbuf);
            exit(1);
        }
        /*Send the packet to network */
        if (pcap_sendpacket(handle, packet, header->len) != 0) {
            perror("ERROR: process_pkt: pcap_sendpacket");
            exit(1);
        }
        pcap_close(handle);
        fprintf(stderr, "Bouncer: packet sent\n");
    } else {
        /* Or put it back on stdout */
        int i = 0;
        for (i = 0; i < ETHER_ADDR_LEN; i++)
            ethernet->ether_shost[i] = 1;
        if(icmp->icmp_type == 0) {
            for (i = 0; i < ETHER_ADDR_LEN; i++)
                ethernet->ether_dhost[i] = 2;
        } else if (icmp->icmp_type == 8) {
            for (i = 0; i < ETHER_ADDR_LEN; i++)
                ethernet->ether_dhost[i] = 3;
        }
        pcap_dump(dumper, header, packet);

////////////////////////////////////////////////////////////////////////
/*
        pcap_t *handle = NULL;
        char errbuf[PCAP_ERRBUF_SIZE], *device = "tap0";
        memset(errbuf, 0, PCAP_ERRBUF_SIZE);
        if ((handle = pcap_open_live(device, MAX_PACKETS_NO, 1, 512, errbuf)) == NULL) {
            fprintf(stderr, "ERROR: %s\n", errbuf);
            exit(1);
        }
        if (pcap_sendpacket(handle, packet, header->len) != 0) {
perror("ERROR: process_pkt: pcap_sendpacket");
            exit(1);
        }
        pcap_close(handle);
        fprintf(stderr, "Packet sent\n");
*/
        ////////////////////////////////////////////////////////////////////////

    }
    return;
}

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

#include "bouncer.h"

/* CRC

* Adopted from <a href="http://www.netfor2.com/ipsum.htm">http://www.netfor2.com/ipsum.htm</a>

typedef unsigned short u16;

typedef unsigned long u32;

u16 ip_sum_calc(u16 len_ip_header, u16 buff[]) {

u16 word16;

u32 sum =0;

u16 i;

// make 16 bit words out of every two adjacent 8 bit words in the packet

// and add them up

for (i = 0; i < len_ip_header; i = i + 2) {

word16 = ((buff[i] << 8)&0xFF00)+(buff[i + 1]&0xFF);

sum = sum + (u32) word16;

}

// take only 16 bits out of the 32 bit sum and add up the carries

while (sum >> 16)

sum = (sum & 0xFFFF)+(sum >> 16);

// one'scomplement the result

sum = ~sum;

return ((u16) sum);

}

void process_pkt(u_char *args, struct pcap_pkthdr *header,

u_char *packet) {

if(header->caplen < header->len){

fprintf(stderr, "ERROR: Packet data not captured completely\n");

return;

}

/* Main function to perform the bouncing */

u_char testmode = *args;

char *serv_addr = (char *) (args + 1);

u_int32_t dst_addr =inet_addr(serv_addr);

//pcap_dumper_t *dumper = NULL;

u_char *dumper = NULL;

memcpy(&dumper, args + 2 + strlen(serv_addr), sizeof (pcap_dumper_t *));

struct request ** prequests = NULL;

memcpy(&prequests, args + 2 + strlen(serv_addr) + sizeof (pcap_dumper_t *), sizeof (struct request**));

//struct request *requests = *prequests;

/* Typecasting packet*/

struct sniff_ethernet *ethernet; /* The ethernet header */

struct sniff_ip *ip; /* The IP header */

struct sniff_icmp *icmp; /* The ICMP header */

char *padding; /* Packet padding */

u_int size_ip;

ethernet = (struct sniff_ethernet*) (packet);

ip = (struct sniff_ip*) (packet + SIZE_ETHERNET);

size_ip = IP_HL(ip)*4;

u_int32_t srcip = ntohl(ip->ip_src.s_addr);

if (size_ip < 20 || size_ip > header->len - SIZE_ETHERNET) {

fprintf(stderr, "ERROR: Invalid IP header length: %ubytes\n", size_ip);

if (testmode == 1) {

header->caplen = 0;

header->len = 0;

pcap_dump(dumper, header, packet);

}

return;

}

icmp = (struct sniff_icmp*) (packet + SIZE_ETHERNET + size_ip);

padding = (u_char *) (packet + SIZE_ETHERNET + size_ip + SIZE_ICMP);

/* Validate the packet */

/* Validate IP header */

/* Check IP version */

u_char v = ip->ip_vhl>> 4;

if(v != 4){

fprintf(stderr, "ERROR: Wrong IP verison %d\n", v);

return;

}

/* Validate CRC */

u16 ipbuf[size_ip];

u16 ipsum = ntohs(ip->ip_sum);

int i;

for (i = 0; i < size_ip; i++) {

if (i == 10 || i == 11)

ipbuf[i] = 0x00;

else

ipbuf[i] = *((u_char *) (packet + SIZE_ETHERNET + i));

}

if (ipsum != ip_sum_calc(size_ip, ipbuf)) {

fprintf(stderr, "ERROR: ip checksum mismatch. Dropping packet from %u.%u.%u.%u\n",

IP_QUAD(srcip));

if (testmode == 1) {

header->caplen = 0;

header->len = 0;

pcap_dump(dumper, header, packet);

}

return;

}

/* Validate TTL */

if (ip->ip_ttl <= 0) {

fprintf(stderr, "ERROR: ip TTL expired. Dropping packet from %u.%u.%u.%u\n",

IP_QUAD(srcip));

if (testmode == 1) {

header->caplen = 0;

header->len = 0;

pcap_dump(dumper, header, packet);

}

return;

}

/* Validate IP source address */

if (srcip == 0x00000000 || srcip >= 0xE0000000

|| (srcip & 0x000000FF) == 0x000000FF || (srcip & 0x000000FF) == 0x00000000) {

fprintf(stderr, "ERROR: ip source address invalid. Dropping packetfrom %u.%u.%u.%u\n",

IP_QUAD(srcip));

if (testmode == 1) {

header->caplen = 0;

header->len = 0;

pcap_dump(dumper, header, packet);

}

return;

}

/* Validate ICMP header */

/* Validate ICMP type and code */

if (!(icmp->icmp_code == 0 && (icmp->icmp_type == 0 || icmp->icmp_type == 8))) {

fprintf(stderr, "ERROR: icmp type orcode unsupported. Dropping packet from %u.%u.%u.%u\n",

IP_QUAD(srcip));

if (testmode == 1) {

header->caplen = 0;

header->len = 0;

pcap_dump(dumper, header, packet);

}

return;

}

/* Validate CRC */

int plen = header->len - SIZE_ETHERNET - size_ip - 8;

u16 icmpbuf[8 + plen];

u16 icmpsum = ntohs(icmp->icmp_sum);

for (i = 0; i < 8;i++) {

if (i == 2 || i == 3)

icmpbuf[i] = 0x00;

else

icmpbuf[i] = *((u_char *) (packet + SIZE_ETHERNET + size_ip + i));

}

for (i = 0; i < plen; i++) {

icmpbuf[i + 8] = *((u_char *) (padding + i));

}

if (icmpsum != ip_sum_calc(8 + plen, icmpbuf)) {

fprintf(stderr, "ERROR: icmp checksum mismatch. Dropping packet from %u.%u.%u.%u\n",

IP_QUAD(srcip));

if(testmode == 1) {

header->caplen = 0;

header->len = 0;

pcap_dump(dumper, header, packet);

}

return;

}

/* Update the packet */

if (icmp->icmp_type == 0) {

/* ICMP echo reply */

ip->ip_src.s_addr = ip->ip_dst.s_addr;

/* Search the linked list for client address */

if (*prequests == NULL) {

fprintf(stderr, "ERROR: process_pkt: nullrequest linked list\n");

return;

} else {

/* Find where the request comes from */

struct request *r;

for (r = *prequests; r != NULL; r = r->next) {

if (r->icmp->icmp_id == icmp->icmp_id && r->icmp->icmp_sequence == icmp->icmp_sequence) {

ip->ip_dst.s_addr = r->ip->ip_src.s_addr;

break;

}

if (r == NULL) {

fprintf(stderr, "ERROR: no match echo requests in stack\n");

return;

}

/* Remove the request from the linked list */

struct request *rr = *prequests;

if (rr == r) {

free(rr->icmp);

free(rr->ip);

*prequests = r->next;

free(r);

} else {

while (rr!= r)

rr = rr->next;

free(rr->icmp);

free(rr->ip);

rr->next = r->next;

free(r);

}

} else {

/* ICMP echo request */

/* Add new request to linked list */

struct request *r;

r = malloc(sizeof (struct request));

if (r == NULL) {

perror("ERROR: process_pkt:malloc");

return;

}

struct sniff_ip *ipt = malloc(sizeof (struct sniff_ip));

if (ipt == NULL) {

perror("ERROR: process_pkt: malloc");

return;

}

memcpy(ipt, ip, sizeof (struct sniff_ip));

r->ip = ipt;

struct sniff_icmp* icmpt = malloc(sizeof (struct sniff_icmp));

if (icmpt == NULL) {

perror("ERROR: process_pkt: malloc");

return;

}

memcpy(icmpt, icmp, sizeof (struct sniff_icmp));

r->icmp = icmpt;

r->next = *prequests;

*prequests = r;

/* Update destination address */

ip->ip_src.s_addr = ip->ip_dst.s_addr;

ip->ip_dst.s_addr = dst_addr;

}

/* Recaculate CRC */

for (i = 0; i < size_ip; i++) {

if (i == 10 || i == 11)

ipbuf[i] = 0x00;

else

ipbuf[i] = *((u_char *) (packet + SIZE_ETHERNET + i));

}

ip->ip_sum = htons(ip_sum_calc(size_ip, ipbuf));

if (testmode == 0) {

pcap_t *handle = NULL;

char errbuf[PCAP_ERRBUF_SIZE], *device = "tap0";

memset(errbuf, 0, PCAP_ERRBUF_SIZE);

if ((handle = pcap_open_live(device, MAX_PACKET_SIZE, 1, 512, errbuf)) == NULL) {

fprintf(stderr, "ERROR: %s\n", errbuf);

exit(1);

}

/*Send the packet to network */

if (pcap_sendpacket(handle, packet, header->len) != 0) {

perror("ERROR: process_pkt: pcap_sendpacket");

exit(1);

}

pcap_close(handle);

fprintf(stderr, "Bouncer: packet sent\n");

} else {

/* Or put it back on stdout */

int i = 0;

for (i = 0; i < ETHER_ADDR_LEN; i++)

ethernet->ether_shost[i] = 1;

if(icmp->icmp_type == 0) {

for (i = 0; i < ETHER_ADDR_LEN; i++)

ethernet->ether_dhost[i] = 2;

} else if (icmp->icmp_type == 8) {

for (i = 0; i < ETHER_ADDR_LEN; i++)

ethernet->ether_dhost[i] = 3;

}

pcap_dump(dumper, header, packet);

////////////////////////////////////////////////////////////////////////

pcap_t *handle = NULL;

char errbuf[PCAP_ERRBUF_SIZE], *device = "tap0";

memset(errbuf, 0, PCAP_ERRBUF_SIZE);

if ((handle = pcap_open_live(device, MAX_PACKETS_NO, 1, 512, errbuf)) == NULL) {

fprintf(stderr, "ERROR: %s\n", errbuf);

exit(1);

}

if (pcap_sendpacket(handle, packet, header->len) != 0) {

perror("ERROR: process_pkt: pcap_sendpacket");

exit(1);

}

pcap_close(handle);

fprintf(stderr, "Packet sent\n");

////////////////////////////////////////////////////////////////////////

}

return;

}

Code

Published 2010/07/08 by Daoyuan Li

The code looks as follows.

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include<ctype.h>
#include <netdb.h>
#include <fcntl.h>
#include <time.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/file.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include "event.h"
#include "rudp.h"
#include "rudp_api.h"

//#define DROP 3

rudp_socket_t rs_head = NULL;

peer_t find_peer(peer_t *firstp, structsockaddr_in* sa) {
    peer_t p;
    //int pc = 0;
    for (p = *firstp; p != NULL; p = p->next) {
        //printf("peer count: %d\n", ++pc);
        if (memcmp(p->sa, sa, sizeof (struct sockaddr_in)) == 0)
            return p;
    }
    //printf("peer not found, creating new peer\n");
    p = malloc(sizeof (struct peer));
    if (p == NULL) {
        perror("find_peer: malloc");
        return NULL;
    }
    struct sockaddr_in*sin;
    sin = malloc(sizeof (struct sockaddr_in));
    if (sin == NULL) {
        perror("peerfind: malloc");
        return NULL;
    }
    memcpy(sin, sa, sizeof (struct sockaddr_in));
    p->sa = sin;
    p->packets = NULL;
    p->status = PEER_STATUS_INIT;
    p->sb = 0;
    p->sm = RUDP_WINDOW - 1;
    p->sn = 0;
    p->next = (*firstp);
    *firstp = p;
    return p;
}

int remove_peer(peer_t *firstp,peer_t rp) {
    peer_t p, *pp;
    pp = firstp;
    for (p = *firstp; p != NULL; p = p->next) {
        if (p == rp) {
            *pp = rp->next;
            free(rp->sa);
            free(rp);
            return 0;
        }
        pp = &p->next;
    }
    return -1;
}

/*
 * Add packet into a linked list.
 * Inserted in a way that packets with smaller seqno are always placed in front
 */
int add_packet(packet_t*packet_head, packet_t *pkt) {
    if (*packet_head == NULL) {
        (*pkt)->next = *packet_head;
        *packet_head = *pkt;
    } else {
        packet_t *p = malloc(sizeof (packet_t));
        for ((*p) = *packet_head; (*p) != NULL; (*p) = (*p)->next) {
            if ((*pkt)->header->seqno == (*p)->header->seqno + 1) {
                (*pkt)->next = (*p)->next;
                (*p)->next = *pkt;
                break;
}
        }
        //return -1;
    }
    //printf("packet added: %d type %d\n", (*pkt)->header->seqno, (*pkt)->header->type);
    return 0;
}

/*
 * Remove a packet from a linked list
 */
int remove_packet(packet_t *packet_head, packet_t pkt) {
    packet_t p, *pp;
    pp = packet_head;
    for (p = *packet_head; p != NULL; p = p->next) {
        if (pkt == p) {
            //printf("packet seq no %d removed\n",pkt->header->seqno);
            *pp = p->next;
            free(p);
            return 0;
        }
        pp = &p->next;
    }
    return -1;
}

/*
 * rudp_socket: Create a RUDP socket.
 * May use a random port by setting port to zero.
 */

rudp_socket_t rudp_socket(int port32) {
    int sockfd;
    sockfd = socket(PF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("rudp_socket: socket");
return NULL;
    }
    struct sockaddr_in *sin;
    sin = malloc(sizeof (struct sockaddr_in));
    if (sin == NULL) {
        perror("rudp_socket: malloc");
        return NULL;
    }
    sin->sin_addr.s_addr = htonl(INADDR_ANY);
    //sin->sin_addr.s_addr = inet_addr("127.0.0.1");
    sin->sin_family = AF_INET;
    uint16_t port = port32;
    if (port == 0) {
        srand(time(0));
        port = (rand() % (65535 - 1024)) + 1024;
sin->sin_port = htons(port);
        while (bind(sockfd, (struct sockaddr*) sin, sizeof (struct sockaddr_in)) < 0) {
            port = (rand() % (65535 - 1024)) + 1024;
            sin->sin_port = htons(port);
        }
    } else {
        sin->sin_port = htons(port);
        if (bind(sockfd, (struct sockaddr*) sin, sizeof (struct sockaddr_in)) < 0) {
            perror("rudp_socket: bind");
            return NULL;
        }
}
    //printf("rudp_socket: bind successfully on port: %d\n", port);
    rudp_socket_t rs;
    rs = malloc(sizeof (struct rudp_socket));
    if (rs == NULL) {
        perror("rudp_socket: malloc");
        return NULL;
    }
    rs->sockfd = sockfd;
    rs->peers = NULL;
    rs->next = rs_head;
    rs_head = rs;
    /*
        int rc = 0;
        rudp_socket_t prs;
        for(prs = rs_head; prs != NULL; prs =prs->next)
            printf("rudp socket count: %d\n", ++rc);
     */
    event_fd(rs->sockfd, rudp_listen, rs, "rudp_listen");
    return rs;
}

/*
 * Listens on the socket
 */
int rudp_listen(int fd, void *arg) {
    rudp_socket_t rs;
    for (rs = rs_head; rs != NULL; rs = rs->next) {
        if (rs->sockfd == fd)
            break;
    }
    if (rs == NULL) {
        return -1;
    }
    int (*handler)(rudp_socket_t,struct sockaddr_in *, char *, int);

    /*
        client_addr.sin_family = AF_INET;
        client_addr.sin_addr.s_addr = htonl(INADDR_ANY);
        client_addr.sin_port = htons(0);
     */
    unsigned int clientlen = sizeof(struct sockaddr);
    struct sockaddr client_sockaddr;
    int bufsize = RUDP_MAXPKTSIZE + sizeof (struct rudp_hdr);
    int msglen = 0;
    char message[bufsize];
    memset(message, 0, bufsize);
    msglen =recvfrom(rs->sockfd, message, bufsize, 0, & client_sockaddr, &clientlen);
    if (msglen < 0) {
        perror("rudp_listen: recvfrom");
        return -1;
    }
    struct sockaddr_in client_addr;
    memcpy(&client_addr, &client_sockaddr, clientlen);
    if (ntohs(client_addr.sin_port) == 0) {
        perror("rudp_listen: recvfrom port 0");
        return -1;
    }
    //printf("received from port: %d\n",ntohs(client_addr.sin_port));
    peer_t p = find_peer(&(rs->peers), &client_addr);
    if (p == NULL) {
        return -1;
    }
    //printf("peer: %d\n", ntohs(p->sa->sin_port));
    if (msglen < 0) {
        perror("rudp_recvfrom: recvfrom");
        return -1;
    } else if (msglen < (sizeof (struct rudp_hdr))) {
        fprintf(stderr, "rudp_recvfrom: error receiving packet");
        return -1;
    }
    structrudp_hdr *msgheader = malloc(sizeof (struct rudp_hdr));
    if (msgheader == NULL) {
        perror("rudp_recvfrom: malloc");
        return -1;
    }
    memcpy(msgheader, message, sizeof (struct rudp_hdr));

    //printf("status=%d sn=%d\n", p->status, p->sn);
    //printf("message from port %d, type=%d seqno=%d\n", ntohs(p->sa->sin_port), msgheader->type, msgheader->seqno);
    struct rudp_hdr *replyheader = malloc(sizeof (structrudp_hdr));
    if (replyheader == NULL) {
        perror("rudp_recvfrom: malloc");
        return -1;
    }
    replyheader->version = RUDP_VERSION;
    switch (p->status) {
        case PEER_STATUS_INIT:
            if (msgheader->type == RUDP_SYN) {
                p->status = PEER_STATUS_ACTIVE;
                p->sn = msgheader->seqno + 1;
                replyheader->seqno = msgheader->seqno + 1;
replyheader->type = RUDP_ACK;
                sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,
                        (struct sockaddr*) & client_addr, clientlen);
                //printf("ACK sent. Turns active\n");
            }
            break;
        case PEER_STATUS_PASSIVE:
            if (msgheader->type == RUDP_ACK && msgheader->seqno == 1) {
                p->status = PEER_STATUS_ACTIVE;
                packet_t pkt;
for (pkt = p->packets; pkt != NULL; pkt = pkt->next) {
                    if (pkt->header->seqno == msgheader->seqno - 1) {
                        pkt->status = ACKED;
                        //printf("syn packet no. %d acked\n", pkt->header->seqno);
                        break;
                    }
                }
                //p->sn = 1;
                p->sb = 1;
                p->sm = RUDP_WINDOW;
    }
            break;
        case PEER_STATUS_ACTIVE:
            switch (msgheader->type) {
                case RUDP_ACK:
                    //printf("sb: %d sm: %d\n", p->sb, p->sm);
                    if (msgheader->seqno >= p->sb) {
                        packet_t pkt;
                        for (pkt = p->packets; pkt != NULL; pkt = pkt->next) {
                            if (pkt->header->seqno == msgheader->seqno -    1) {
                                pkt->status = ACKED;
                                //printf("data packet no. %d acked\n", pkt->header->seqno);
                                break;
                            }
                        }
                        p->sm += msgheader->seqno - p->sb;
                        p->sb = msgheader->seqno;
                    }
                    break;
    case RUDP_DATA:
#ifdef DROP
                    srand(time(0));
                    if (rand() % DROP == 0) {
                        printf("packet dropped\n");
                        break;
                    }
#endif
                    if (msgheader->seqno == p->sn) {
                        p->sn = msgheader->seqno + 1;
                        replyheader->seqno = msgheader->seqno + 1;
    replyheader->type = RUDP_ACK;
                        handler = malloc(sizeof (int (*)()));
                        if (handler == NULL) {
                            perror("rudp_listen: malloc");
                            return -1;
                        }
                        handler = (int (*)(rudp_socket_t, struct sockaddr_in*, char *, int))arg;
                        void *data;
                        data = malloc(msglen -    sizeof (struct rudp_hdr));
                        if (data == NULL) {
                            perror("rudp_listen: malloc");
                            return -1;
                        }
                        memcpy(data, message + sizeof (struct rudp_hdr),
                                msglen - sizeof (struct rudp_hdr));
                        handler(rs, &client_addr, data, msglen - sizeof (struct    rudp_hdr));
                        sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,
                                (struct sockaddr*) & client_addr, clientlen);
                    }
                    break;
                case RUDP_SYN:
                    p->status = PEER_STATUS_ACTIVE;
                    p->sn = msgheader->seqno + 1;
                    replyheader->seqno = msgheader->seqno + 1;
    replyheader->type = RUDP_ACK;
                    sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,
                            (struct sockaddr*) & client_addr, clientlen);
                    break;
                case RUDP_FIN:
                    p->status = PEER_STATUS_CLOSED;
                    p->sn = msgheader->seqno + 1;
                    replyheader->seqno = msgheader->seqno + 1;
    replyheader->type = RUDP_ACK;
                    sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,
                            (struct sockaddr*) & client_addr, clientlen);
                    break;
                default:
                    fprintf(stderr, "rudp_listen: invalid RUDP type %d\n",
                            msgheader->type);
                    break;
            }
            break;
        case    PEER_STATUS_CLOSING:
            if (msgheader->type == RUDP_ACK && msgheader->seqno == p->sn + 1) {
                p->status = PEER_STATUS_CLOSED;
                //printf("peer closed\n");
            }
            break;
        case PEER_STATUS_CLOSED:
            if (msgheader->type == RUDP_FIN) {
                p->status = PEER_STATUS_CLOSED;
                p->sn = msgheader->seqno + 1;
    replyheader->seqno = msgheader->seqno + 1;
                replyheader->type = RUDP_ACK;
                sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,
                        (struct sockaddr*) & client_addr, clientlen);
            }
            /*
                        if (msgheader->type == RUDP_SYN) {
                            p->status = PEER_STATUS_ACTIVE;
    p->sn = msgheader->seqno + 1;
                            replyheader->seqno = msgheader->seqno + 1;
                            replyheader->type = RUDP_ACK;
                            sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,
                                    (struct sockaddr*) & client_addr, clientlen);
                        } else if (msgheader->type == RUDP_FIN) {
                            p->status =    PEER_STATUS_CLOSED;
                            p->sn = msgheader->seqno + 1;
                            replyheader->seqno = msgheader->seqno + 1;
                            replyheader->type = RUDP_ACK;
                            sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,
                                    (struct sockaddr*) & client_addr, clientlen);
                        }
             */
            break;
    default:
            fprintf(stderr, "rudp_listen: invalid peer status %d\n",
                    p->status);
            break;
    }
    return 0;
}

/*
 * Keep checking if there are packets to be sent out
 */
int rudp_send(int fd, void *arg) {
    event_timeout_delete(rudp_send, arg);
    struct timeval now, interval, t;
    gettimeofday(&now, NULL);
    interval.tv_sec = 0;
    interval.tv_usec = RUDP_CHECK_INTERVAL;
    timeradd(&now, &interval, &t);
    rudp_socket_t rs;
    peer_t p;
    packet_t pkt;
    void *msg;
    int len = sizeof (struct rudp_hdr);
    //int rsc = 0;
    if (rs_head == NULL) {
        return 0;
    }
    for (rs = rs_head; rs != NULL; rs = rs->next) {
        //printf("rudp socket count: %d\n", ++rsc);
        for (p = rs->peers; p != NULL; p = p->next) {
            if (p->status == PEER_STATUS_CLOSED) {
    if (remove_peer(&(rs->peers), p) < 0) {
                    perror("rudp_send: remove_peer");
                    return -1;
                } else {
                    event_timeout(t, rudp_send, NULL, "rudp_send");
                }
                return 0;
            } else if (p->status != PEER_STATUS_ACTIVE) {
                event_timeout(t, rudp_send, NULL, "rudp_send");
                return 0;
            }
        //int pc = 0;
            for (pkt = p->packets; pkt != NULL; pkt = pkt->next) {
                //printf("pakcet %d: seq number %d status %d\n", ++pc, pkt->header->seqno, pkt->status);
                if (pkt->status == ACKED) {
                    if (remove_packet(&(p->packets), pkt) == -1) {
                        return -1;
                    }
                    event_timeout(t, rudp_send, NULL, "rudp_send");
        return 0;
                }
                if ((pkt->status == IN_QUEUE || pkt->status == TIMEOUT) &&
                        pkt->header->seqno >= p->sb &&
                        pkt->header->seqno <= p->sm) {
                    if (pkt->header->type == RUDP_FIN) {
                        p->status = PEER_STATUS_CLOSING;
                    }
                    len = sizeof (struct        rudp_hdr) + pkt->datalen;
                    msg = malloc(len);
                    if (msg == NULL) {
                        perror("rudp_send: malloc");
                        return -1;
                    }
                    memcpy(msg, pkt->header, sizeof (struct rudp_hdr));
                    memcpy(msg + sizeof (struct rudp_hdr), pkt->data, pkt->datalen);
                    sendto(rs->sockfd, msg,        len, 0,
                            (struct sockaddr*) p->sa, sizeof (struct sockaddr));
                    pkt->status = SENT;
                    pkt->trans_count++;
                    struct timeval now, interval, t;
                    gettimeofday(&now, NULL);
                    if (RUDP_TIMEOUT >= 1000) {
                        interval.tv_sec = RUDP_TIMEOUT / 1000;
                        interval.tv_usec = 0;
        } else {
                        interval.tv_sec = 0;
                        interval.tv_usec = RUDP_TIMEOUT * 1000;
                    }
                    timeradd(&now, &interval, &t);
                    event_timeout(t, rudp_timeout, pkt, "rudp_timeout");
                }

            }
        }
    }
    event_timeout(t, rudp_send, NULL, "rudp_send");
    return 0;
}

int rudp_timeout(int a, void *arg) {
        packet_t pkt = (packet_t) arg;
    event_timeout_delete(rudp_timeout, pkt);
    if (pkt->status != ACKED) {
        //printf("Timeout: %d\n", pkt->header->seqno);
        pkt->status = TIMEOUT;
        if (pkt->trans_count >= RUDP_MAXRETRANS)
            pkt->status = FAILED;
    }
    return 0;
}

/*
 *rudp_close: Close socket
 */

int rudp_close(rudp_socket_t rsocket) {

    struct timeval now, interval,        t;
    gettimeofday(&now, NULL);
    interval.tv_sec = 0;
    interval.tv_usec = RUDP_CHECK_INTERVAL;
    timeradd(&now, &interval, &t);
    event_timeout(t, rudp_close_session, rsocket, "rudp_close_socket");
    return 0;
    /*
        peer_t p;
        packet_t pkt;
        struct rudp_hdr *hdr;
        hdr = malloc(sizeof (struct rudp_hdr));
        if (hdr == NULL) {
            perror("rudp_sendto: malloc");
        return -1;
        }
        pkt = malloc(sizeof (struct packet));
        if (pkt == NULL) {
            perror("rudp_sendto: malloc");
            return -1;
        }
        for (p = rsocket->peers; p != NULL; p = p->next) {
            hdr->version = RUDP_VERSION;
            hdr->type = RUDP_FIN;
            hdr->seqno = p->sn++;
            pkt->data = NULL;
            pkt->datalen = 0;
        pkt->header = hdr;
            pkt->next = NULL;
            pkt->trans_count = 0;
            pkt->status = IN_QUEUE;
            if (add_packet(&p->packets, &pkt) < 0) {
                perror("rudp_sendto: add_packet");
                return -1;
            }
        }
        return 0;
     */
}

int rudp_close_session(int fd, void *arg) {
    event_timeout_delete(rudp_close_session, arg);
    rudp_socket_t rs        = (rudp_socket_t) arg;
    peer_t p;
    //printf("closing rudp socket %d\n", rs->sockfd);
    //printf("peer: %p\n", rs->peers);
    if (rs->peers == NULL) {
        //printf("peer null\n");
        event_fd_delete(rudp_listen, rs);
        close(rs->sockfd);
        rudp_socket_t r, *rr;
        rr = &rs_head;
        for (r = rs_head; r != NULL; r = r->next) {
            if (r == rs) {
                *rr = r->next;
        free(r);
                return 0;
            }
            rr = &r->next;
        }
        return -1;
    }
    //printf("peers not null\n");
    for (p = rs->peers; p != NULL; p = p->next) {
        //check if there are still packets to be sent
        if (p->packets != NULL) {
            struct timeval now, interval, t;
            gettimeofday(&now, NULL);
            interval.tv_sec = 0;
        interval.tv_usec = RUDP_CHECK_INTERVAL;
            timeradd(&now, &interval, &t);
            event_timeout(t, rudp_close_session, arg, "rudp_close_socket");
            return 0;
        }
        //printf("no packets in this peer, status %d\n", p->status);
        if (p->status != PEER_STATUS_CLOSED) {
            p->status = PEER_STATUS_CLOSING;
            struct rudp_hdr header;
            header.seqno = p->sn;
        header.type = RUDP_FIN;
            header.version = RUDP_VERSION;
            sendto(rs->sockfd, &header, sizeof (struct rudp_hdr), 0,
                    (struct sockaddr*) p->sa, sizeof (struct sockaddr_in));
            struct timeval now, interval, t;
            gettimeofday(&now, NULL);
            if (RUDP_TIMEOUT >= 1000) {
                interval.tv_sec = RUDP_TIMEOUT / 1000;
                interval.tv_usec = 0;
        } else {
                interval.tv_sec = 0;
                interval.tv_usec = RUDP_TIMEOUT * 1000;
            }
            timeradd(&now, &interval, &t);
            event_timeout(t, rudp_close_session, arg, "rudp_close_socket");
            //printf("FIN sent, check again 2s later\n");
            return 0;
        }
        //printf("peer status closed\n");
        if (remove_peer(&(rs->peers), p) < 0)        {
            perror("rudp_close_session: remove_peer");
            return -1;
        } else {
            //printf("peer successfully removed\n");
            struct timeval now, interval, t;
            gettimeofday(&now, NULL);
            interval.tv_sec = 0;
            interval.tv_usec = RUDP_CHECK_INTERVAL;
            timeradd(&now, &interval, &t);
            event_timeout(t, rudp_close_session, arg, "rudp_close_socket");
        return 0;
        }
    }
    return 0;
}

/*
 *rudp_recvfrom_handler: Register receive callback function
 */

int rudp_recvfrom_handler(rudp_socket_t rsocket,
        int (*handler)(rudp_socket_t, struct sockaddr_in *,
        char *, int)) {
    event_fd(rsocket->sockfd, rudp_listen, handler, "rudp_listen");
    event_fd_delete(rudp_listen, rsocket);
    return 0;
}

/*
 *rudp_event_handler: Register event handler        callback function
 */
int rudp_event_handler(rudp_socket_t rsocket,
        int (*handler)(rudp_socket_t, rudp_event_t,
        struct sockaddr_in *)) {
    struct timeval now, interval, t;
    gettimeofday(&now, NULL);
    interval.tv_sec = 0;
    interval.tv_usec = RUDP_CHECK_INTERVAL;
    timeradd(&now, &interval, &t);
    event_timeout(t, rudp_check_status, handler, "rudp_check_status");
    return 0;
}

int        rudp_check_status(int fd, void * arg) {
    event_timeout_delete(rudp_check_status, arg);
    int (*handler)(rudp_socket_t, rudp_event_t, struct sockaddr_in *);
    handler = (int (*)(rudp_socket_t, rudp_event_t, struct sockaddr_in *))arg;
    rudp_socket_t rs;
    peer_t p;
    packet_t pkt;
    for (rs = rs_head; rs != NULL; rs = rs->next) {
        for (p = rs->peers; p != NULL; p = p->next) {
            if (p->status == PEER_STATUS_CLOSED)        {
                handler(rs, RUDP_EVENT_CLOSED, p->sa);
                if (remove_peer(&(rs->peers), p) < 0)
                    return -1;
                return 0;
            }
            for (pkt = p->packets; pkt != NULL; pkt = pkt->next) {
                if (pkt->status == FAILED) {
                    handler(rs, RUDP_EVENT_TIMEOUT, p->sa);
                    if (remove_peer(&(rs->peers), p) < 0)
        return -1;
                    return 0;
                }
            }
        }
    }
    struct timeval now, interval, t;
    gettimeofday(&now, NULL);
    interval.tv_sec = 0;
    interval.tv_usec = RUDP_CHECK_INTERVAL;
    timeradd(&now, &interval, &t);
    event_timeout(t, rudp_check_status, handler, "rudp_check_status");
    return 0;
}

/*
 * rudp_sendto: Send a block of data to the receiver.
        */

int rudp_sendto(rudp_socket_t rsocket, void* data, int len, struct sockaddr_in* to) {
    peer_t p;
    packet_t pkt;
    struct rudp_hdr *hdr;
    hdr = malloc(sizeof (struct rudp_hdr));
    if (hdr == NULL) {
        perror("rudp_sendto: malloc");
        return -1;
    }
    pkt = malloc(sizeof (struct packet));
    if (pkt == NULL) {
        perror("rudp_sendto: malloc");
        return -1;
    }
    p =        find_peer(&(rsocket->peers), to);
    if (p == NULL) {
        perror("rudp_sendto: find_peer");
        return -1;
    }
    if (p->status == PEER_STATUS_INIT) {
        rudp_setup_session(0, p);
    }
    hdr = malloc(sizeof (struct rudp_hdr));
    if (hdr == NULL) {
        perror("rudp_sendto: malloc");
        return -1;
    }
    pkt = malloc(sizeof (struct packet));
    if (pkt == NULL) {
        perror("rudp_sendto: malloc");
        return -1;
    }
    hdr->version = RUDP_VERSION;
    hdr->type = RUDP_DATA;
    hdr->seqno = p->sn++;
    pkt->data = malloc(len);
    if (pkt->data == NULL) {
        perror("rudp_sendto: malloc");
        return -1;
    }
    memcpy(pkt->data, data, len);
    pkt->datalen = len;
    pkt->header = hdr;
    pkt->next = NULL;
    pkt->trans_count = 0;
        pkt->status = IN_QUEUE;
    //printf("adding packet %d to %d\n", pkt->header->seqno, ntohs(p->sa->sin_port));
    if (add_packet(&p->packets, &pkt) < 0) {
        perror("rudp_sendto: add_packet");
        return -1;
    }
    return 0;
}

int rudp_setup_session(int fd, void *arg) {
    event_timeout_delete(rudp_setup_session, arg);
    peer_t p = (peer_t) arg;
    if (p == NULL) {
        perror("rudp_setup_session: error finding peer");
        return -1;
    }
    int sockfd;
    rudp_socket_t rs;
    peer_t pp;
    int flag = 0;
    for (rs = rs_head; rs != NULL; rs = rs->next) {
        for (pp = rs->peers; pp != NULL; pp = pp->next) {
            if (pp == p) {
                sockfd = rs->sockfd;
                flag = 1;
                break;
            }
        }
        if (flag == 1)
        break;
    }
    struct rudp_hdr header;
    header.seqno = p->sn++;
    header.type = RUDP_SYN;
    header.version = RUDP_VERSION;
    sendto(sockfd, &header, sizeof (struct rudp_hdr), 0,
            (struct sockaddr*) p->sa, sizeof (struct sockaddr_in));
    p->status = PEER_STATUS_PASSIVE;

    struct timeval now, interval, t;
    gettimeofday(&now, NULL);
    if (RUDP_TIMEOUT >= 1000) {
        interval.tv_sec        = RUDP_TIMEOUT / 1000;
        interval.tv_usec = 0;
    } else {
        interval.tv_sec = 0;
        interval.tv_usec = RUDP_TIMEOUT * 1000;
    }
    timeradd(&now, &interval, &t);
    event_timeout(t, rudp_session_check, arg, "rudp_timeout");


    gettimeofday(&now, NULL);
    interval.tv_sec = 0;
    interval.tv_usec = RUDP_CHECK_INTERVAL;
    timeradd(&now, &interval, &t);
    event_timeout(t,        rudp_send, NULL, "rudp_send");
    return 0;
}

int rudp_session_check(int fd, void *arg) {
    event_timeout_delete(rudp_session_check, arg);
    peer_t p = (peer_t) arg;
    if (p == NULL) {
        perror("rudp_setup_session: error finding peer");
        return -1;
    }
    if (p->status == PEER_STATUS_PASSIVE) {
        struct timeval now, interval, t;
        gettimeofday(&now, NULL);
        interval.tv_usec = 0;
        interval.tv_sec = 0;
        timeradd(&now, &interval, &t);
        event_timeout(t, rudp_setup_session, arg, "rudp_setup_session");
    }
    return 0;
}

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

148

149

150

151

152

153

154

155

156

157

158

159

160

161

162

163

164

165

166

167

168

169

170

171

172

173

174

175

176

177

178

179

180

181

182

183

184

185

186

187

188

189

190

191

192

193

194

195

196

197

198

199

200

201

202

203

204

205

206

207

208

209

210

211

212

213

214

215

216

217

218

219

220

221

222

223

224

225

226

227

228

229

230

231

232

233

234

235

236

237

238

239

240

241

242

243

244

245

246

247

248

249

250

251

252

253

254

255

256

257

258

259

260

261

262

263

264

265

266

267

268

269

270

271

272

273

274

275

276

277

278

279

280

281

282

283

284

285

286

287

288

289

290

291

292

293

294

295

296

297

298

299

300

301

302

303

304

305

306

307

308

309

310

311

312

313

314

315

316

317

318

319

320

321

322

323

324

325

326

327

328

329

330

331

332

333

334

335

336

337

338

339

340

341

342

343

344

345

346

347

348

349

350

351

352

353

354

355

356

357

358

359

360

361

362

363

364

365

366

367

368

369

370

371

372

373

374

375

376

377

378

379

380

381

382

383

384

385

386

387

388

389

390

391

392

393

394

395

396

397

398

399

400

401

402

403

404

405

406

407

408

409

410

411

412

413

414

415

416

417

418

419

420

421

422

423

424

425

426

427

428

429

430

431

432

433

434

435

436

437

438

439

440

441

442

443

444

445

446

447

448

449

450

451

452

453

454

455

456

457

458

459

460

461

462

463

464

465

466

467

468

469

470

471

472

473

474

475

476

477

478

479

480

481

482

483

484

485

486

487

488

489

490

491

492

493

494

495

496

497

498

499

500

501

502

503

504

505

506

507

508

509

510

511

512

513

514

515

516

517

518

519

520

521

522

523

524

525

526

527

528

529

530

531

532

533

534

535

536

537

538

539

540

541

542

543

544

545

546

547

548

549

550

551

552

553

554

555

556

557

558

559

560

561

562

563

564

565

566

567

568

569

570

571

572

573

574

575

576

577

578

579

580

581

582

583

584

585

586

587

588

589

590

591

592

593

594

595

596

597

598

599

600

601

602

603

604

605

606

607

608

609

610

611

612

613

614

615

616

617

618

619

620

621

622

623

624

625

626

627

628

629

630

631

632

633

634

635

636

637

638

639

640

641

642

643

644

645

646

647

648

649

650

651

652

653

654

655

656

657

658

659

660

661

662

663

664

665

666

667

668

669

670

671

672

673

674

675

676

677

678

679

680

681

682

683

684

685

686

687

688

689

690

691

692

693

694

695

696

697

698

699

700

701

702

703

704

705

706

707

708

709

710

711

712

713

714

715

716

717

718

719

720

721

722

723

724

725

726

727

728

729

730

731

732

733

734

735

736

737

738

739

740

741

742

743

744

745

746

747

748

749

750

751

752

753

754

755

756

757

758

759

760

761

762

763

764

765

766

767

768

769

770

771

772

773

774

#include <unistd.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include<ctype.h>

#include <netdb.h>

#include <fcntl.h>

#include <time.h>

#include <sys/types.h>

#include <sys/time.h>

#include <sys/file.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include "event.h"

#include "rudp.h"

#include "rudp_api.h"

//#define DROP 3

rudp_socket_t rs_head = NULL;

peer_t find_peer(peer_t *firstp, structsockaddr_in* sa) {

peer_t p;

//int pc = 0;

for (p = *firstp; p != NULL; p = p->next) {

//printf("peer count: %d\n", ++pc);

if (memcmp(p->sa, sa, sizeof (struct sockaddr_in)) == 0)

return p;

}

//printf("peer not found, creating new peer\n");

p = malloc(sizeof (struct peer));

if (p == NULL) {

perror("find_peer: malloc");

return NULL;

}

struct sockaddr_in*sin;

sin = malloc(sizeof (struct sockaddr_in));

if (sin == NULL) {

perror("peerfind: malloc");

return NULL;

}

memcpy(sin, sa, sizeof (struct sockaddr_in));

p->sa = sin;

p->packets = NULL;

p->status = PEER_STATUS_INIT;

p->sb = 0;

p->sm = RUDP_WINDOW - 1;

p->sn = 0;

p->next = (*firstp);

*firstp = p;

return p;

}

int remove_peer(peer_t *firstp,peer_t rp) {

peer_t p, *pp;

pp = firstp;

for (p = *firstp; p != NULL; p = p->next) {

if (p == rp) {

*pp = rp->next;

free(rp->sa);

free(rp);

return 0;

}

pp = &p->next;

}

return -1;

}

* Add packet into a linked list.

* Inserted in a way that packets with smaller seqno are always placed in front

int add_packet(packet_t*packet_head, packet_t *pkt) {

if (*packet_head == NULL) {

(*pkt)->next = *packet_head;

*packet_head = *pkt;

} else {

packet_t *p = malloc(sizeof (packet_t));

for ((*p) = *packet_head; (*p) != NULL; (*p) = (*p)->next) {

if ((*pkt)->header->seqno == (*p)->header->seqno + 1) {

(*pkt)->next = (*p)->next;

(*p)->next = *pkt;

break;

}

//return -1;

}

//printf("packet added: %d type %d\n", (*pkt)->header->seqno, (*pkt)->header->type);

return 0;

}

* Remove a packet from a linked list

int remove_packet(packet_t *packet_head, packet_t pkt) {

packet_t p, *pp;

pp = packet_head;

for (p = *packet_head; p != NULL; p = p->next) {

if (pkt == p) {

//printf("packet seq no %d removed\n",pkt->header->seqno);

*pp = p->next;

free(p);

return 0;

}

pp = &p->next;

}

return -1;

}

* rudp_socket: Create a RUDP socket.

* May use a random port by setting port to zero.

rudp_socket_t rudp_socket(int port32) {

int sockfd;

sockfd = socket(PF_INET, SOCK_DGRAM, 0);

if (sockfd < 0) {

perror("rudp_socket: socket");

return NULL;

}

struct sockaddr_in *sin;

sin = malloc(sizeof (struct sockaddr_in));

if (sin == NULL) {

perror("rudp_socket: malloc");

return NULL;

}

sin->sin_addr.s_addr = htonl(INADDR_ANY);

//sin->sin_addr.s_addr = inet_addr("127.0.0.1");

sin->sin_family = AF_INET;

uint16_t port = port32;

if (port == 0) {

srand(time(0));

port = (rand() % (65535 - 1024)) + 1024;

sin->sin_port = htons(port);

while (bind(sockfd, (struct sockaddr*) sin, sizeof (struct sockaddr_in)) < 0) {

port = (rand() % (65535 - 1024)) + 1024;

sin->sin_port = htons(port);

}

} else {

sin->sin_port = htons(port);

if (bind(sockfd, (struct sockaddr*) sin, sizeof (struct sockaddr_in)) < 0) {

perror("rudp_socket: bind");

return NULL;

}

//printf("rudp_socket: bind successfully on port: %d\n", port);

rudp_socket_t rs;

rs = malloc(sizeof (struct rudp_socket));

if (rs == NULL) {

perror("rudp_socket: malloc");

return NULL;

}

rs->sockfd = sockfd;

rs->peers = NULL;

rs->next = rs_head;

rs_head = rs;

int rc = 0;

rudp_socket_t prs;

for(prs = rs_head; prs != NULL; prs =prs->next)

printf("rudp socket count: %d\n", ++rc);

event_fd(rs->sockfd, rudp_listen, rs, "rudp_listen");

return rs;

}

* Listens on the socket

int rudp_listen(int fd, void *arg) {

rudp_socket_t rs;

for (rs = rs_head; rs != NULL; rs = rs->next) {

if (rs->sockfd == fd)

break;

}

if (rs == NULL) {

return -1;

}

int (*handler)(rudp_socket_t,struct sockaddr_in *, char *, int);

client_addr.sin_family = AF_INET;

client_addr.sin_addr.s_addr = htonl(INADDR_ANY);

client_addr.sin_port = htons(0);

unsigned int clientlen = sizeof(struct sockaddr);

struct sockaddr client_sockaddr;

int bufsize = RUDP_MAXPKTSIZE + sizeof (struct rudp_hdr);

int msglen = 0;

char message[bufsize];

memset(message, 0, bufsize);

msglen =recvfrom(rs->sockfd, message, bufsize, 0, & client_sockaddr, &clientlen);

if (msglen < 0) {

perror("rudp_listen: recvfrom");

return -1;

}

struct sockaddr_in client_addr;

memcpy(&client_addr, &client_sockaddr, clientlen);

if (ntohs(client_addr.sin_port) == 0) {

perror("rudp_listen: recvfrom port 0");

return -1;

}

//printf("received from port: %d\n",ntohs(client_addr.sin_port));

peer_t p = find_peer(&(rs->peers), &client_addr);

if (p == NULL) {

return -1;

}

//printf("peer: %d\n", ntohs(p->sa->sin_port));

if (msglen < 0) {

perror("rudp_recvfrom: recvfrom");

return -1;

} else if (msglen < (sizeof (struct rudp_hdr))) {

fprintf(stderr, "rudp_recvfrom: error receiving packet");

return -1;

}

structrudp_hdr *msgheader = malloc(sizeof (struct rudp_hdr));

if (msgheader == NULL) {

perror("rudp_recvfrom: malloc");

return -1;

}

memcpy(msgheader, message, sizeof (struct rudp_hdr));

//printf("status=%d sn=%d\n", p->status, p->sn);

//printf("message from port %d, type=%d seqno=%d\n", ntohs(p->sa->sin_port), msgheader->type, msgheader->seqno);

struct rudp_hdr *replyheader = malloc(sizeof (structrudp_hdr));

if (replyheader == NULL) {

perror("rudp_recvfrom: malloc");

return -1;

}

replyheader->version = RUDP_VERSION;

switch (p->status) {

case PEER_STATUS_INIT:

if (msgheader->type == RUDP_SYN) {

p->status = PEER_STATUS_ACTIVE;

p->sn = msgheader->seqno + 1;

replyheader->seqno = msgheader->seqno + 1;

replyheader->type = RUDP_ACK;

sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,

(struct sockaddr*) & client_addr, clientlen);

//printf("ACK sent. Turns active\n");

}

break;

case PEER_STATUS_PASSIVE:

if (msgheader->type == RUDP_ACK && msgheader->seqno == 1) {

p->status = PEER_STATUS_ACTIVE;

packet_t pkt;

for (pkt = p->packets; pkt != NULL; pkt = pkt->next) {

if (pkt->header->seqno == msgheader->seqno - 1) {

pkt->status = ACKED;

//printf("syn packet no. %d acked\n", pkt->header->seqno);

break;

}

//p->sn = 1;

p->sb = 1;

p->sm = RUDP_WINDOW;

}

break;

case PEER_STATUS_ACTIVE:

switch (msgheader->type) {

case RUDP_ACK:

//printf("sb: %d sm: %d\n", p->sb, p->sm);

if (msgheader->seqno >= p->sb) {

packet_t pkt;

for (pkt = p->packets; pkt != NULL; pkt = pkt->next) {

if (pkt->header->seqno == msgheader->seqno - 1) {

pkt->status = ACKED;

//printf("data packet no. %d acked\n", pkt->header->seqno);

break;

}

p->sm += msgheader->seqno - p->sb;

p->sb = msgheader->seqno;

}

break;

case RUDP_DATA:

#ifdef DROP

srand(time(0));

if (rand() % DROP == 0) {

printf("packet dropped\n");

break;

}

#endif

if (msgheader->seqno == p->sn) {

p->sn = msgheader->seqno + 1;

replyheader->seqno = msgheader->seqno + 1;

replyheader->type = RUDP_ACK;

handler = malloc(sizeof (int (*)()));

if (handler == NULL) {

perror("rudp_listen: malloc");

return -1;

}

handler = (int (*)(rudp_socket_t, struct sockaddr_in*, char *, int))arg;

void *data;

data = malloc(msglen - sizeof (struct rudp_hdr));

if (data == NULL) {

perror("rudp_listen: malloc");

return -1;

}

memcpy(data, message + sizeof (struct rudp_hdr),

msglen - sizeof (struct rudp_hdr));

handler(rs, &client_addr, data, msglen - sizeof (struct rudp_hdr));

sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,

(struct sockaddr*) & client_addr, clientlen);

}

break;

case RUDP_SYN:

p->status = PEER_STATUS_ACTIVE;

p->sn = msgheader->seqno + 1;

replyheader->seqno = msgheader->seqno + 1;

replyheader->type = RUDP_ACK;

sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,

(struct sockaddr*) & client_addr, clientlen);

break;

case RUDP_FIN:

p->status = PEER_STATUS_CLOSED;

p->sn = msgheader->seqno + 1;

replyheader->seqno = msgheader->seqno + 1;

replyheader->type = RUDP_ACK;

sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,

(struct sockaddr*) & client_addr, clientlen);

break;

default:

fprintf(stderr, "rudp_listen: invalid RUDP type %d\n",

msgheader->type);

break;

}

break;

case PEER_STATUS_CLOSING:

if (msgheader->type == RUDP_ACK && msgheader->seqno == p->sn + 1) {

p->status = PEER_STATUS_CLOSED;

//printf("peer closed\n");

}

break;

case PEER_STATUS_CLOSED:

if (msgheader->type == RUDP_FIN) {

p->status = PEER_STATUS_CLOSED;

p->sn = msgheader->seqno + 1;

replyheader->seqno = msgheader->seqno + 1;

replyheader->type = RUDP_ACK;

sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,

(struct sockaddr*) & client_addr, clientlen);

}

if (msgheader->type == RUDP_SYN) {

p->status = PEER_STATUS_ACTIVE;

p->sn = msgheader->seqno + 1;

replyheader->seqno = msgheader->seqno + 1;

replyheader->type = RUDP_ACK;

sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,

(struct sockaddr*) & client_addr, clientlen);

} else if (msgheader->type == RUDP_FIN) {

p->status = PEER_STATUS_CLOSED;

p->sn = msgheader->seqno + 1;

replyheader->seqno = msgheader->seqno + 1;

replyheader->type = RUDP_ACK;

sendto(fd, replyheader, sizeof (struct rudp_hdr), 0,

(struct sockaddr*) & client_addr, clientlen);

}

break;

default:

fprintf(stderr, "rudp_listen: invalid peer status %d\n",

p->status);

break;

}

return 0;

}

* Keep checking if there are packets to be sent out

int rudp_send(int fd, void *arg) {

event_timeout_delete(rudp_send, arg);

struct timeval now, interval, t;

gettimeofday(&now, NULL);

interval.tv_sec = 0;

interval.tv_usec = RUDP_CHECK_INTERVAL;

timeradd(&now, &interval, &t);

rudp_socket_t rs;

peer_t p;

packet_t pkt;

void *msg;

int len = sizeof (struct rudp_hdr);

//int rsc = 0;

if (rs_head == NULL) {

return 0;

}

for (rs = rs_head; rs != NULL; rs = rs->next) {

//printf("rudp socket count: %d\n", ++rsc);

for (p = rs->peers; p != NULL; p = p->next) {

if (p->status == PEER_STATUS_CLOSED) {

if (remove_peer(&(rs->peers), p) < 0) {

perror("rudp_send: remove_peer");

return -1;

} else {

event_timeout(t, rudp_send, NULL, "rudp_send");

}

return 0;

} else if (p->status != PEER_STATUS_ACTIVE) {

event_timeout(t, rudp_send, NULL, "rudp_send");

return 0;

}

//int pc = 0;

for (pkt = p->packets; pkt != NULL; pkt = pkt->next) {

//printf("pakcet %d: seq number %d status %d\n", ++pc, pkt->header->seqno, pkt->status);

if (pkt->status == ACKED) {

if (remove_packet(&(p->packets), pkt) == -1) {

return -1;

}

event_timeout(t, rudp_send, NULL, "rudp_send");

return 0;

}

if ((pkt->status == IN_QUEUE || pkt->status == TIMEOUT) &&

pkt->header->seqno >= p->sb &&

pkt->header->seqno <= p->sm) {

if (pkt->header->type == RUDP_FIN) {

p->status = PEER_STATUS_CLOSING;

}

len = sizeof (struct rudp_hdr) + pkt->datalen;

msg = malloc(len);

if (msg == NULL) {

perror("rudp_send: malloc");

return -1;

}

memcpy(msg, pkt->header, sizeof (struct rudp_hdr));

memcpy(msg + sizeof (struct rudp_hdr), pkt->data, pkt->datalen);

sendto(rs->sockfd, msg, len, 0,

(struct sockaddr*) p->sa, sizeof (struct sockaddr));

pkt->status = SENT;

pkt->trans_count++;

struct timeval now, interval, t;

gettimeofday(&now, NULL);

if (RUDP_TIMEOUT >= 1000) {

interval.tv_sec = RUDP_TIMEOUT / 1000;

interval.tv_usec = 0;

} else {

interval.tv_sec = 0;

interval.tv_usec = RUDP_TIMEOUT * 1000;

}

timeradd(&now, &interval, &t);

event_timeout(t, rudp_timeout, pkt, "rudp_timeout");

}

event_timeout(t, rudp_send, NULL, "rudp_send");

return 0;

}

int rudp_timeout(int a, void *arg) {

packet_t pkt = (packet_t) arg;

event_timeout_delete(rudp_timeout, pkt);

if (pkt->status != ACKED) {

//printf("Timeout: %d\n", pkt->header->seqno);

pkt->status = TIMEOUT;

if (pkt->trans_count >= RUDP_MAXRETRANS)

pkt->status = FAILED;

}

return 0;

}

*rudp_close: Close socket

int rudp_close(rudp_socket_t rsocket) {

struct timeval now, interval, t;

gettimeofday(&now, NULL);

interval.tv_sec = 0;

interval.tv_usec = RUDP_CHECK_INTERVAL;

timeradd(&now, &interval, &t);

event_timeout(t, rudp_close_session, rsocket, "rudp_close_socket");

return 0;

peer_t p;

packet_t pkt;

struct rudp_hdr *hdr;

hdr = malloc(sizeof (struct rudp_hdr));

if (hdr == NULL) {

perror("rudp_sendto: malloc");

return -1;

}

pkt = malloc(sizeof (struct packet));

if (pkt == NULL) {

perror("rudp_sendto: malloc");

return -1;

}

for (p = rsocket->peers; p != NULL; p = p->next) {

hdr->version = RUDP_VERSION;

hdr->type = RUDP_FIN;

hdr->seqno = p->sn++;

pkt->data = NULL;

pkt->datalen = 0;

pkt->header = hdr;

pkt->next = NULL;

pkt->trans_count = 0;

pkt->status = IN_QUEUE;

if (add_packet(&p->packets, &pkt) < 0) {

perror("rudp_sendto: add_packet");

return -1;

}

return 0;

}

int rudp_close_session(int fd, void *arg) {

event_timeout_delete(rudp_close_session, arg);

rudp_socket_t rs = (rudp_socket_t) arg;

peer_t p;

//printf("closing rudp socket %d\n", rs->sockfd);

//printf("peer: %p\n", rs->peers);

if (rs->peers == NULL) {

//printf("peer null\n");

event_fd_delete(rudp_listen, rs);

close(rs->sockfd);

rudp_socket_t r, *rr;

rr = &rs_head;

for (r = rs_head; r != NULL; r = r->next) {

if (r == rs) {

*rr = r->next;

free(r);

return 0;

}

rr = &r->next;

}

return -1;

}

//printf("peers not null\n");

for (p = rs->peers; p != NULL; p = p->next) {

//check if there are still packets to be sent

if (p->packets != NULL) {

struct timeval now, interval, t;

gettimeofday(&now, NULL);

interval.tv_sec = 0;

interval.tv_usec = RUDP_CHECK_INTERVAL;

timeradd(&now, &interval, &t);

event_timeout(t, rudp_close_session, arg, "rudp_close_socket");

return 0;

}

//printf("no packets in this peer, status %d\n", p->status);

if (p->status != PEER_STATUS_CLOSED) {

p->status = PEER_STATUS_CLOSING;

struct rudp_hdr header;

header.seqno = p->sn;

header.type = RUDP_FIN;

header.version = RUDP_VERSION;

sendto(rs->sockfd, &header, sizeof (struct rudp_hdr), 0,

(struct sockaddr*) p->sa, sizeof (struct sockaddr_in));

struct timeval now, interval, t;

gettimeofday(&now, NULL);

if (RUDP_TIMEOUT >= 1000) {

interval.tv_sec = RUDP_TIMEOUT / 1000;

interval.tv_usec = 0;

} else {

interval.tv_sec = 0;

interval.tv_usec = RUDP_TIMEOUT * 1000;

}

timeradd(&now, &interval, &t);

event_timeout(t, rudp_close_session, arg, "rudp_close_socket");

//printf("FIN sent, check again 2s later\n");

return 0;

}

//printf("peer status closed\n");

if (remove_peer(&(rs->peers), p) < 0) {

perror("rudp_close_session: remove_peer");

return -1;

} else {

//printf("peer successfully removed\n");

struct timeval now, interval, t;

gettimeofday(&now, NULL);

interval.tv_sec = 0;

interval.tv_usec = RUDP_CHECK_INTERVAL;

timeradd(&now, &interval, &t);

event_timeout(t, rudp_close_session, arg, "rudp_close_socket");

return 0;

}

return 0;

}

*rudp_recvfrom_handler: Register receive callback function

int rudp_recvfrom_handler(rudp_socket_t rsocket,

int (*handler)(rudp_socket_t, struct sockaddr_in *,

char *, int)) {

event_fd(rsocket->sockfd, rudp_listen, handler, "rudp_listen");

event_fd_delete(rudp_listen, rsocket);

return 0;

}

*rudp_event_handler: Register event handler callback function

int rudp_event_handler(rudp_socket_t rsocket,

int (*handler)(rudp_socket_t, rudp_event_t,

struct sockaddr_in *)) {

struct timeval now, interval, t;

gettimeofday(&now, NULL);

interval.tv_sec = 0;

interval.tv_usec = RUDP_CHECK_INTERVAL;

timeradd(&now, &interval, &t);

event_timeout(t, rudp_check_status, handler, "rudp_check_status");

return 0;

}

int rudp_check_status(int fd, void * arg) {

event_timeout_delete(rudp_check_status, arg);

int (*handler)(rudp_socket_t, rudp_event_t, struct sockaddr_in *);

handler = (int (*)(rudp_socket_t, rudp_event_t, struct sockaddr_in *))arg;

rudp_socket_t rs;

peer_t p;

packet_t pkt;

for (rs = rs_head; rs != NULL; rs = rs->next) {

for (p = rs->peers; p != NULL; p = p->next) {

if (p->status == PEER_STATUS_CLOSED) {

handler(rs, RUDP_EVENT_CLOSED, p->sa);

if (remove_peer(&(rs->peers), p) < 0)

return -1;

return 0;

}

for (pkt = p->packets; pkt != NULL; pkt = pkt->next) {

if (pkt->status == FAILED) {

handler(rs, RUDP_EVENT_TIMEOUT, p->sa);

if (remove_peer(&(rs->peers), p) < 0)

return -1;

return 0;

}

struct timeval now, interval, t;

gettimeofday(&now, NULL);

interval.tv_sec = 0;

interval.tv_usec = RUDP_CHECK_INTERVAL;

timeradd(&now, &interval, &t);

event_timeout(t, rudp_check_status, handler, "rudp_check_status");

return 0;

}

* rudp_sendto: Send a block of data to the receiver.

int rudp_sendto(rudp_socket_t rsocket, void* data, int len, struct sockaddr_in* to) {

peer_t p;

packet_t pkt;

struct rudp_hdr *hdr;

hdr = malloc(sizeof (struct rudp_hdr));

if (hdr == NULL) {

perror("rudp_sendto: malloc");

return -1;

}

pkt = malloc(sizeof (struct packet));

if (pkt == NULL) {

perror("rudp_sendto: malloc");

return -1;

}

p = find_peer(&(rsocket->peers), to);

if (p == NULL) {

perror("rudp_sendto: find_peer");

return -1;

}

if (p->status == PEER_STATUS_INIT) {

rudp_setup_session(0, p);

}

hdr = malloc(sizeof (struct rudp_hdr));

if (hdr == NULL) {

perror("rudp_sendto: malloc");

return -1;

}

pkt = malloc(sizeof (struct packet));

if (pkt == NULL) {

perror("rudp_sendto: malloc");

return -1;

}

hdr->version = RUDP_VERSION;

hdr->type = RUDP_DATA;

hdr->seqno = p->sn++;

pkt->data = malloc(len);

if (pkt->data == NULL) {

perror("rudp_sendto: malloc");

return -1;

}

memcpy(pkt->data, data, len);

pkt->datalen = len;

pkt->header = hdr;

pkt->next = NULL;

pkt->trans_count = 0;

pkt->status = IN_QUEUE;

//printf("adding packet %d to %d\n", pkt->header->seqno, ntohs(p->sa->sin_port));

if (add_packet(&p->packets, &pkt) < 0) {

perror("rudp_sendto: add_packet");

return -1;

}

return 0;

}

int rudp_setup_session(int fd, void *arg) {

event_timeout_delete(rudp_setup_session, arg);

peer_t p = (peer_t) arg;

if (p == NULL) {

perror("rudp_setup_session: error finding peer");

return -1;

}

int sockfd;

rudp_socket_t rs;

peer_t pp;

int flag = 0;

for (rs = rs_head; rs != NULL; rs = rs->next) {

for (pp = rs->peers; pp != NULL; pp = pp->next) {

if (pp == p) {

sockfd = rs->sockfd;

flag = 1;

break;

}

if (flag == 1)

break;

}

struct rudp_hdr header;

header.seqno = p->sn++;

header.type = RUDP_SYN;

header.version = RUDP_VERSION;

sendto(sockfd, &header, sizeof (struct rudp_hdr), 0,

(struct sockaddr*) p->sa, sizeof (struct sockaddr_in));

p->status = PEER_STATUS_PASSIVE;

struct timeval now, interval, t;

gettimeofday(&now, NULL);

if (RUDP_TIMEOUT >= 1000) {

interval.tv_sec = RUDP_TIMEOUT / 1000;

interval.tv_usec = 0;

} else {

interval.tv_sec = 0;

interval.tv_usec = RUDP_TIMEOUT * 1000;

}

timeradd(&now, &interval, &t);

event_timeout(t, rudp_session_check, arg, "rudp_timeout");

gettimeofday(&now, NULL);

interval.tv_sec = 0;

interval.tv_usec = RUDP_CHECK_INTERVAL;

timeradd(&now, &interval, &t);

event_timeout(t, rudp_send, NULL, "rudp_send");

return 0;

}

int rudp_session_check(int fd, void *arg) {

event_timeout_delete(rudp_session_check, arg);

peer_t p = (peer_t) arg;

if (p == NULL) {

perror("rudp_setup_session: error finding peer");

return -1;

}

if (p->status == PEER_STATUS_PASSIVE) {

struct timeval now, interval, t;

gettimeofday(&now, NULL);

interval.tv_usec = 0;

interval.tv_sec = 0;

timeradd(&now, &interval, &t);

event_timeout(t, rudp_setup_session, arg, "rudp_setup_session");

}

return 0;

}