中财网神兵玄奇之南宫铁心h:traceroute，C源代码实现
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路由跟踪原理，traceroute，C源代码实现
Traceroute允许我们确定IP数据报从本地主机游历到某个远地主机所经过的路径。它使用IPv4的TTL字段或IP
v6的跳字段以及两种ICMP消息。它一开始向目的地发送一个TTL（或跳限）为1的UDP数据报。这个数据报导致第一跳路由器返送一个ICMP“time exceeded in transit(传输中超时)”错误。它接着没递增TTL一次发送一个UDP数据报，从而逐步确定下一个路由器。当某个UDP数据报到达最终目的地时，目标是由这个主机返送一个ICMP “port unreachable(端口不可达)”错误。这个目标通过向一个随机选取的但愿未被目的地主机使用的端口发送UDP数据报得以实现。
早期版本的traceroute程序只能通过设置IP_HDRINCL套接口选项直接构造自己的IPv4头部来设置TTL字段。然而如今的系统却提供IP_TTL套接口选项，它允许我们指定外出数据报所用的TTL。（这个套接口选项随4.3BSD Reno 版本引入。）设置这个套接口选项比构造完整的IPv4头容易的多。IPv6的IPV6_UNICAST_HOPS套接口选项允许我们控制IPv6数据报的跳限字段。
注意：该程序运行时需要root权限！
以下便是在该原理指导下的C源代码实现：
/*
yongsheng zhang 20081010
*/
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define BUFSIZE 1500
struct rec /* format of outgoing UDP data */
{
u_short rec_seq; /* sequence number */
u_short rec_ttl; /* TTL packet left with */
struct timeval rec_tv; /* time packet left */
char msg[32]; /*message*/
};
/* globals */
char recvbuf[BUFSIZE]; /*receive databuffer*/
char sendbuf[BUFSIZE]; /*send databuffer*/
int datalen; /* # bytes of data following ICMP header */
char *host; /* local hostname/IP */
u_short sport, dport; /* source and destination */
int nsent; /* add 1 for each sendto() */
pid_t pid; /* our PID */
int probe, nprobes; /* groups */
int sendfd, recvfd; /* send on UDP sock, read on raw ICMP sock */
int gotalarm;
int optind;//获得在argv[]中的索引
/* function prototypes */
const char *icmpcode_v4(int);/* determine the diffrent conditions when routing */
int recv_v4(int, struct timeval *);
void sig_alrm(int);/*timer-signal */
void traceloop(void);/* main loop */
void tv_sub(struct timeval *, struct timeval *);/* calculate tima */
char *Sock_ntop_host(const struct sockaddr *sa, socklen_t salen);/* change the netseq to hostseq */
char *sock_ntop_host(const struct sockaddr *sa, socklen_t salen);/* change the netseq to hostseq */
void sock_set_port(struct sockaddr *sa, socklen_t salen, int port);/* set port */
int sock_cmp_addr(const struct sockaddr *sa1, const struct sockaddr *sa2,socklen_t salen);/* compare the last IP with this time */
struct addrinfo *Host_serv(const char *host, const char *serv, int family, int socktype);/* get the destination IP */
struct proto
{
const char *(*icmpcode)(int);/* pointer which point to function icmpcode_v4()*/
int (*recv)(int, struct timeval *);/* pointer which point to function recv_v4() */
struct sockaddr *sasend; /* sockaddr{} for send, from getaddrinfo */
struct sockaddr *sarecv; /* sockaddr{} for receiving */
struct sockaddr *salast; /* last sockaddr{} for receiving */
struct sockaddr *sabind; /* sockaddr{} for binding source port */
socklen_t salen; /* length of sockaddr{}s */
int icmpproto; /* IPPROTO_xxx value for ICMP */
int ttllevel; /* setsockopt() level to set TTL */
int ttloptname; /* setsockopt() name to set TTL */
} *pr;
struct proto proto_v4 = { icmpcode_v4, recv_v4, NULL, NULL, NULL, NULL, 0,
IPPROTO_ICMP, IPPROTO_IP, IP_TTL };/* init struct proto */
int datalen = sizeof(struct rec); /* defaults */
int max_ttl = 30;/* the max nops */
int nprobes = 3;/* three groups */
u_short dport = 32768 + 666;/* desthost port which not want to be connected */
int main(int argc, char **argv)
{
int c;
struct addrinfo *ai;
char *h;
/*getopt(argc, argv, "a");*/
if (argc!=2)
{
perror("usage: traceroute");
return 0;
}
host = argv[optind];/* get IP/hostname */
signal(SIGALRM, sig_alrm);/* send signal and set gotalarm */
ai = Host_serv(host, NULL, AF_INET, 0);/* get the destination IP */
h = Sock_ntop_host(ai->ai_addr, ai->ai_addrlen);/* change the netseq to hostseq */
printf("traceroute to %s (%s): %d hops max, %d byte packets\n",/* print */
ai->ai_canonname ? ai->ai_canonname : h,
h, max_ttl, datalen);
/* initialize according to protocol */
if (ai->ai_family == AF_INET) {/* if it is IPv4 ,then pr=&proto */
pr = &proto_v4;
} else/* else print error massage */
printf("unknown address family %d", ai->ai_family);
pr->sasend = ai->ai_addr; /* contains destination address */
pr->sarecv = calloc(1, ai->ai_addrlen);
pr->salast = calloc(1, ai->ai_addrlen);
pr->sabind = calloc(1, ai->ai_addrlen);
pr->salen = ai->ai_addrlen;
traceloop();/* call main loop function */
exit(0);
}
const char *icmpcode_v4(int code)/* determine the diffrent conditions when routing */
{
static char errbuf[100];
switch (code) {
case 0: return("network unreachable");
case 1: return("host unreachable");
case 2: return("protocol unreachable");
case 3: return("port unreachable");
case 4: return("fragmentation required but DF bit set");
case 5: return("source route failed");
case 6: return("destination network unknown");
case 7: return("destination host unknown");
case 8: return("source host isolated (obsolete)");
case 9: return("destination network administratively prohibited");
case 10: return("destination host administratively prohibited");
case 11: return("network unreachable for TOS");
case 12: return("host unreachable for TOS");
case 13: return("communication administratively prohibited by filtering");
case 14: return("host recedence violation");
case 15: return("precedence cutoff in effect");
default: sprintf(errbuf, "[unknown code %d]", code);
return errbuf;
}
}
void sig_alrm(int signo)
{
gotalarm = 1; /* set flag to note that alarm occurred */
return; /* and interrupt the recvfrom() */
}
void traceloop(void)/* mian loop */
{
int seq, code, done;
double rtt;
int ttl;
struct rec *rec;
struct timeval tvrecv;
char *str;
recvfd = socket(pr->sasend->sa_family, SOCK_RAW, pr->icmpproto);/* SOCK_RAW */
if(recvfd==-1)
{
perror("socket error");
exit(0);
}
setuid(getuid()); /* don't need special permissions anymore */
sendfd = socket(pr->sasend->sa_family, SOCK_DGRAM, 0);/* SOCK_DGRAM */
pr->sabind->sa_family = pr->sasend->sa_family;/* init */
sport = (getpid() & 0xffff) | 0x8000; /* our source UDP port # */
sock_set_port(pr->sabind, pr->salen, htons(sport));
bind(sendfd, pr->sabind, pr->salen);/*bind UDP socket with source port*/
sig_alrm(SIGALRM);/*build signal de*/
seq = 0;
done = 0;
for (ttl = 1; ttl <= max_ttl && done == 0; ttl++) {
setsockopt(sendfd, pr->ttllevel, pr->ttloptname, &ttl, sizeof(int));
bzero(pr->salast, pr->salen);
printf("%2d ", ttl);
fflush(stdout);
for (probe = 0; probe < nprobes; probe++) {
rec = (struct rec *) sendbuf;
rec->rec_seq = ++seq;
rec->rec_ttl = ttl;
gettimeofday(&rec->rec_tv, NULL);
sock_set_port(pr->sasend, pr->salen, htons(dport + seq));
sendto(sendfd, sendbuf, datalen, 0, pr->sasend, pr->salen);
if ( (code = (*pr->recv)(seq, &tvrecv)) == -3)
printf(" *"); /* timeout, no reply */
else {
char str[NI_MAXHOST];
if (sock_cmp_addr(pr->sarecv, pr->salast, pr->salen) != 0) {
if (getnameinfo(pr->sarecv, pr->salen, str, sizeof(str),
NULL, 0, 0) == 0)
printf(" %s (%s)", str,
sock_ntop_host(pr->sarecv, pr->salen));
else
printf(" %s",
sock_ntop_host(pr->sarecv, pr->salen));
memcpy(pr->salast, pr->sarecv, pr->salen);
}
tv_sub(&tvrecv, &rec->rec_tv);
rtt = tvrecv.tv_sec * 1000.0 + tvrecv.tv_usec / 1000.0;
printf(" %.3f ms", rtt);
if (code == -1) /* port unreachable; at destination */
done++;
else if (code >= 0)
printf(" (ICMP %s)", (*pr->icmpcode)(code));
}
fflush(stdout);
}
printf("\n");
}
}
void tv_sub(struct timeval *out, struct timeval *in)
{
if ( (out->tv_usec -= in->tv_usec) < 0) { /* out -= in */
--out->tv_sec;
out->tv_usec += 1000000;
}
out->tv_sec -= in->tv_sec;
}
struct addrinfo *Host_serv(const char *host, const char *serv, int family, int socktype)
{
int n;
struct addrinfo hints, *res;
bzero(&hints, sizeof(struct addrinfo));
hints.ai_flags = AI_CANONNAME; /* always return canonical name */
hints.ai_family = family; /* 0, AF_INET, AF_INET6, etc. */
hints.ai_socktype = socktype; /* 0, SOCK_STREAM, SOCK_DGRAM, etc. */
if ( (n = getaddrinfo(host, serv, &hints, &res)) != 0)
printf("host_serv error for %s, %s: %s",
(host == NULL) ? "(no hostname)" : host,
(serv == NULL) ? "(no service name)" : serv,
gai_strerror(n));
return(res); /* return pointer to first on linked list */
}
/*
return: -3 on timeout
-2 on ICMP time exceeded in transit (caller keeps going)
-1 on ICMP port unreachable (caller is done)
>= return value is some other ICMP unreachable code
*/
int recv_v4(int seq, struct timeval *tv)
{
int hlen1, hlen2, icmplen, ret;
socklen_t len;
ssize_t n;
struct ip *ip, *hip;
struct icmp *icmp;
struct udphdr *udp;
gotalarm = 0;
alarm(3);
for ( ; ; ) {
if (gotalarm)
return(-3); /* alarm expired */
len = pr->salen;
n = recvfrom(recvfd, recvbuf, sizeof(recvbuf), 0, pr->sarecv, &len);
if (n < 0) {
if (errno == EINTR)
continue;
else
perror("recvfrom error");
}
ip = (struct ip *) recvbuf; /* start of IP header */
hlen1 = ip->ip_hl << 2; /* length of IP header */
icmp = (struct icmp *) (recvbuf + hlen1); /* start of ICMP header */
if ( (icmplen = n - hlen1) < 8)
continue; /* not enough to look at ICMP header */
if (icmp->icmp_type == ICMP_TIMXCEED &&
icmp->icmp_code == ICMP_TIMXCEED_INTRANS) {
if (icmplen < 8 + sizeof(struct ip))
continue; /* not enough data to look at inner IP */
hip = (struct ip *) (recvbuf + hlen1 + 8);
hlen2 = hip->ip_hl << 2;
if (icmplen < 8 + hlen2 + 4)
continue; /* not enough data to look at UDP ports */
udp = (struct udphdr *) (recvbuf + hlen1 + 8 + hlen2);
if (hip->ip_p == IPPROTO_UDP &&
udp->source == htons(sport) &&
udp->dest == htons(dport + seq)) {
ret = -2; /* we hit an intermediate router */
break;
}
} else if (icmp->icmp_type == ICMP_UNREACH) {
if (icmplen < 8 + sizeof(struct ip))
continue; /* not enough data to look at inner IP */
hip = (struct ip *) (recvbuf + hlen1 + 8);
hlen2 = hip->ip_hl << 2;
if (icmplen < 8 + hlen2 + 4)
continue; /* not enough data to look at UDP ports */
udp = (struct udphdr *) (recvbuf + hlen1 + 8 + hlen2);
if (hip->ip_p == IPPROTO_UDP &&
udp->source == htons(sport) &&
udp->dest == htons(dport + seq)) {
if (icmp->icmp_code == ICMP_UNREACH_PORT)
ret = -1; /* have reached destination */
else
ret = icmp->icmp_code; /* 0, 1, 2, ... */
break;
}
}
/* Some other ICMP error, recvfrom() again */
}
alarm(0); /* don't leave alarm running */
gettimeofday(tv, NULL); /* get time of packet arrival */
return(ret);
}
char *sock_ntop_host(const struct sockaddr *sa, socklen_t salen)
{
static char str[128]; /* Unix domain is largest */
if (sa->sa_family==AF_INET) {
struct sockaddr_in *sin = (struct sockaddr_in *) sa;
if (inet_ntop(AF_INET, &sin->sin_addr, str, sizeof(str)) == 0)
return(NULL);
return(str);
}
else
{
snprintf(str, sizeof(str), "sock_ntop_host: unknown AF_xxx: %d, len %d",
sa->sa_family, salen);
return(str);
}
return (NULL);
}
char *Sock_ntop_host(const struct sockaddr *sa, socklen_t salen)
{
char *ptr;
if ( (ptr = sock_ntop_host(sa, salen)) == NULL)
perror("sock_ntop_host error"); /* inet_ntop() sets errno */
return(ptr);
}
void sock_set_port(struct sockaddr *sa, socklen_t salen, int port)
{
if (sa->sa_family==AF_INET)
{
struct sockaddr_in *sin = (struct sockaddr_in *) sa;
sin->sin_port = port;
return;
}
return;
}
int sock_cmp_addr(const struct sockaddr *sa1, const struct sockaddr *sa2,socklen_t salen)
{
if (sa1->sa_family != sa2->sa_family)
return(-1);
if(sa1->sa_family==AF_INET) {
return(memcmp( &((struct sockaddr_in *) sa1)->sin_addr,
&((struct sockaddr_in *) sa2)->sin_addr,
sizeof(struct in_addr)));
}
return (-1);
}
Traceroute允许我们确定IP数据报从本地主机游历到某个远地主机所经过的路径。它使用IPv4的TTL字段或IP
v6的跳字段以及两种ICMP消息。它一开始向目的地发送一个TTL（或跳限）为1的UDP数据报。这个数据报导致第一跳路由器返送一个ICMP“time exceeded in transit(传输中超时)”错误。它接着没递增TTL一次发送一个UDP数据报，从而逐步确定下一个路由器。当某个UDP数据报到达最终目的地时，目标是由这个主机返送一个ICMP “port unreachable(端口不可达)”错误。这个目标通过向一个随机选取的但愿未被目的地主机使用的端口发送UDP数据报得以实现。
早期版本的traceroute程序只能通过设置IP_HDRINCL套接口选项直接构造自己的IPv4头部来设置TTL字段。然而如今的系统却提供IP_TTL套接口选项，它允许我们指定外出数据报所用的TTL。（这个套接口选项随4.3BSD Reno 版本引入。）设置这个套接口选项比构造完整的IPv4头容易的多。IPv6的IPV6_UNICAST_HOPS套接口选项允许我们控制IPv6数据报的跳限字段。
注意：该程序运行时需要root权限！
以下便是在该原理指导下的C源代码实现：
/*
yongsheng zhang 20081010
*/
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define BUFSIZE 1500
struct rec /* format of outgoing UDP data */
{
u_short rec_seq; /* sequence number */
u_short rec_ttl; /* TTL packet left with */
struct timeval rec_tv; /* time packet left */
char msg[32]; /*message*/
};
/* globals */
char recvbuf[BUFSIZE]; /*receive databuffer*/
char sendbuf[BUFSIZE]; /*send databuffer*/
int datalen; /* # bytes of data following ICMP header */
char *host; /* local hostname/IP */
u_short sport, dport; /* source and destination */
int nsent; /* add 1 for each sendto() */
pid_t pid; /* our PID */
int probe, nprobes; /* groups */
int sendfd, recvfd; /* send on UDP sock, read on raw ICMP sock */
int gotalarm;
int optind;//获得
/* function prototypes */
const char *icmpcode_v4(int);/* determine the diffrent conditions when routing */
int recv_v4(int, struct timeval *);
void sig_alrm(int);/*timer-signal */
void traceloop(void);/* main loop */
void tv_sub(struct timeval *, struct timeval *);/* calculate tima */
char *Sock_ntop_host(const struct sockaddr *sa, socklen_t salen);/* change the netseq to hostseq */
char *sock_ntop_host(const struct sockaddr *sa, socklen_t salen);/* change the netseq to hostseq */
void sock_set_port(struct sockaddr *sa, socklen_t salen, int port);/* set port */
int sock_cmp_addr(const struct sockaddr *sa1, const struct sockaddr *sa2,socklen_t salen);/* compare the last IP with this time */
struct addrinfo *Host_serv(const char *host, const char *serv, int family, int socktype);/* get the destination IP */
struct proto
{
const char *(*icmpcode)(int);/* pointer which point to function icmpcode_v4()*/
int (*recv)(int, struct timeval *);/* pointer which point to function recv_v4() */
struct sockaddr *sasend; /* sockaddr{} for send, from getaddrinfo */
struct sockaddr *sarecv; /* sockaddr{} for receiving */
struct sockaddr *salast; /* last sockaddr{} for receiving */
struct sockaddr *sabind; /* sockaddr{} for binding source port */
socklen_t salen; /* length of sockaddr{}s */
int icmpproto; /* IPPROTO_xxx value for ICMP */
int ttllevel; /* setsockopt() level to set TTL */
int ttloptname; /* setsockopt() name to set TTL */
} *pr;
struct proto proto_v4 = { icmpcode_v4, recv_v4, NULL, NULL, NULL, NULL, 0,
IPPROTO_ICMP, IPPROTO_IP, IP_TTL };/* init struct proto */
int datalen = sizeof(struct rec); /* defaults */
int max_ttl = 30;/* the max nops */
int nprobes = 3;/* three groups */
u_short dport = 32768 + 666;/* desthost port which not want to be connected */
int main(int argc, char **argv)
{
int c;
struct addrinfo *ai;
char *h;
/*getopt(argc, argv, "a");*/
if (argc!=2)
{
perror("usage: traceroute
return 0;
}
host = argv[optind];/* get IP/hostname */
signal(SIGALRM, sig_alrm);/* send signal and set gotalarm */
ai = Host_serv(host, NULL, AF_INET, 0);/* get the destination IP */
h = Sock_ntop_host(ai->ai_addr, ai->ai_addrlen);/* change the netseq to hostseq */
printf("traceroute to %s (%s): %d hops max, %d byte packets\n",/* print */
ai->ai_canonname ? ai->ai_canonname : h,
h, max_ttl, datalen);
/* initialize according to protocol */
if (ai->ai_family == AF_INET) {/* if it is IPv4 ,then pr=&proto */
pr = &proto_v4;
} else/* else print error massage */
printf("unknown address family %d", ai->ai_family);
pr->sasend = ai->ai_addr; /* contains destination address */
pr->sarecv = calloc(1, ai->ai_addrlen);
pr->salast = calloc(1, ai->ai_addrlen);
pr->sabind = calloc(1, ai->ai_addrlen);
pr->salen = ai->ai_addrlen;
traceloop();/* call main loop function */
exit(0);
}
const char *icmpcode_v4(int code)/* determine the diffrent conditions when routing */
{
static char errbuf[100];
switch (code) {
case 0: return("network unreachable");
case 1: return("host unreachable");
case 2: return("protocol unreachable");
case 3: return("port unreachable");
case 4: return("fragmentation required but DF bit set");
case 5: return("source route failed");
case 6: return("destination network unknown");
case 7: return("destination host unknown");
case 8: return("source host isolated (obsolete)");
case 9: return("destination network administratively prohibited");
case 10: return("destination host administratively prohibited");
case 11: return("network unreachable for TOS");
case 12: return("host unreachable for TOS");
case 13: return("communication administratively prohibited by filtering");
case 14: return("host recedence violation");
case 15: return("precedence cutoff in effect");
default: sprintf(errbuf, "[unknown code %d]", code);
return errbuf;
}
}
void sig_alrm(int signo)
{
gotalarm = 1; /* set flag to note that alarm occurred */
return; /* and interrupt the recvfrom() */
}
void traceloop(void)/* mian loop */
{
int seq, code, done;
double rtt;
int ttl;
struct rec *rec;
struct timeval tvrecv;
char *str;
recvfd = socket(pr->sasend->sa_family, SOCK_RAW, pr->icmpproto);/* SOCK_RAW */
if(recvfd==-1)
{
perror("socket error");
exit(0);
}
setuid(getuid()); /* don't need special permissions anymore */
sendfd = socket(pr->sasend->sa_family, SOCK_DGRAM, 0);/* SOCK_DGRAM */
pr->sabind->sa_family = pr->sasend->sa_family;/* init */
sport = (getpid() & 0xffff) | 0x8000; /* our source UDP port # */
sock_set_port(pr->sabind, pr->salen, htons(sport));
bind(sendfd, pr->sabind, pr->salen);/*bind UDP socket with source port*/
sig_alrm(SIGALRM);/*build signal de*/
seq = 0;
done = 0;
for (ttl = 1; ttl <= max_ttl && done == 0; ttl++) {
setsockopt(sendfd, pr->ttllevel, pr->ttloptname, &ttl, sizeof(int));
bzero(pr->salast, pr->salen);
printf("%2d ", ttl);
fflush(stdout);
for (probe = 0; probe < nprobes; probe++) {
rec = (struct rec *) sendbuf;
rec->rec_seq = ++seq;
rec->rec_ttl = ttl;
gettimeofday(&rec->rec_tv, NULL);
sock_set_port(pr->sasend, pr->salen, htons(dport + seq));
sendto(sendfd, sendbuf, datalen, 0, pr->sasend, pr->salen);
if ( (code = (*pr->recv)(seq, &tvrecv)) == -3)
printf(" *"); /* timeout, no reply */
else {
char str[NI_MAXHOST];
if (sock_cmp_addr(pr->sarecv, pr->salast, pr->salen) != 0) {
if (getnameinfo(pr->sarecv, pr->salen, str, sizeof(str),
NULL, 0, 0) == 0)
printf(" %s (%s)", str,
sock_ntop_host(pr->sarecv, pr->salen));
else
printf(" %s",
sock_ntop_host(pr->sarecv, pr->salen));
memcpy(pr->salast, pr->sarecv, pr->salen);
}
tv_sub(&tvrecv, &rec->rec_tv);
rtt = tvrecv.tv_sec * 1000.0 + tvrecv.tv_usec / 1000.0;
printf(" %.3f ms", rtt);
if (code == -1) /* port unreachable; at destination */
done++;
else if (code >= 0)
printf(" (ICMP %s)", (*pr->icmpcode)(code));
}
fflush(stdout);
}
printf("\n");
}
}
void tv_sub(struct timeval *out, struct timeval *in)
{
if ( (out->tv_usec -= in->tv_usec) < 0) { /* out -= in */
--out->tv_sec;
out->tv_usec += 1000000;
}
out->tv_sec -= in->tv_sec;
}
struct addrinfo *Host_serv(const char *host, const char *serv, int family, int socktype)
{
int n;
struct addrinfo hints, *res;
bzero(&hints, sizeof(struct addrinfo));
hints.ai_flags = AI_CANONNAME; /* always return canonical name */
hints.ai_family = family; /* 0, AF_INET, AF_INET6, etc. */
hints.ai_socktype = socktype; /* 0, SOCK_STREAM, SOCK_DGRAM, etc. */
if ( (n = getaddrinfo(host, serv, &hints, &res)) != 0)
printf("host_serv error for %s, %s: %s",
(host == NULL) ? "(no hostname)" : host,
(serv == NULL) ? "(no service name)" : serv,
gai_strerror(n));
return(res); /* return pointer to first on linked list */
}
/*
return: -3 on timeout
-2 on ICMP time exceeded in transit (caller keeps going)
-1 on ICMP port unreachable (caller is done)
>= return value is some other ICMP unreachable code
*/
int recv_v4(int seq, struct timeval *tv)
{
int hlen1, hlen2, icmplen, ret;
socklen_t len;
ssize_t n;
struct ip *ip, *hip;
struct icmp *icmp;
struct udphdr *udp;
gotalarm = 0;
alarm(3);
for ( ; ; ) {
if (gotalarm)
return(-3); /* alarm expired */
len = pr->salen;
n = recvfrom(recvfd, recvbuf, sizeof(recvbuf), 0, pr->sarecv, &len);
if (n < 0) {
if (errno == EINTR)
continue;
else
perror("recvfrom error");
}
ip = (struct ip *) recvbuf; /* start of IP header */
hlen1 = ip->ip_hl << 2; /* length of IP header */
icmp = (struct icmp *) (recvbuf + hlen1); /* start of ICMP header */
if ( (icmplen = n - hlen1) < 8)
continue; /* not enough to look at ICMP header */
if (icmp->icmp_type == ICMP_TIMXCEED &&
icmp->icmp_code == ICMP_TIMXCEED_INTRANS) {
if (icmplen < 8 + sizeof(struct ip))
continue; /* not enough data to look at inner IP */
hip = (struct ip *) (recvbuf + hlen1 + 8);
hlen2 = hip->ip_hl << 2;
if (icmplen < 8 + hlen2 + 4)
continue; /* not enough data to look at UDP ports */
udp = (struct udphdr *) (recvbuf + hlen1 + 8 + hlen2);
if (hip->ip_p == IPPROTO_UDP &&
udp->source == htons(sport) &&
udp->dest == htons(dport + seq)) {
ret = -2; /* we hit an intermediate router */
break;
}
} else if (icmp->icmp_type == ICMP_UNREACH) {
if (icmplen < 8 + sizeof(struct ip))
continue; /* not enough data to look at inner IP */
hip = (struct ip *) (recvbuf + hlen1 + 8);
hlen2 = hip->ip_hl << 2;
if (icmplen < 8 + hlen2 + 4)
continue; /* not enough data to look at UDP ports */
udp = (struct udphdr *) (recvbuf + hlen1 + 8 + hlen2);
if (hip->ip_p == IPPROTO_UDP &&
udp->source == htons(sport) &&
udp->dest == htons(dport + seq)) {
if (icmp->icmp_code == ICMP_UNREACH_PORT)
ret = -1; /* have reached destination */
else
ret = icmp->icmp_code; /* 0, 1, 2, ... */
break;
}
}
/* Some other ICMP error, recvfrom() again */
}
alarm(0); /* don't leave alarm running */
gettimeofday(tv, NULL); /* get time of packet arrival */
return(ret);
}
char *sock_ntop_host(const struct sockaddr *sa, socklen_t salen)
{
static char str[128]; /* Unix domain is largest */
if (sa->sa_family==AF_INET) {
struct sockaddr_in *sin = (struct sockaddr_in *) sa;
if (inet_ntop(AF_INET, &sin->sin_addr, str, sizeof(str)) == 0)
return(NULL);
return(str);
}
else
{
snprintf(str, sizeof(str), "sock_ntop_host: unknown AF_xxx: %d, len %d",
sa->sa_family, salen);
return(str);
}
return (NULL);
}
char *Sock_ntop_host(const struct sockaddr *sa, socklen_t salen)
{
char *ptr;
if ( (ptr = sock_ntop_host(sa, salen)) == NULL)
perror("sock_ntop_host error"); /* inet_ntop() sets errno */
return(ptr);
}
void sock_set_port(struct sockaddr *sa, socklen_t salen, int port)
{
if (sa->sa_family==AF_INET)
{
struct sockaddr_in *sin = (struct sockaddr_in *) sa;
sin->sin_port = port;
return;
}
return;
}
int sock_cmp_addr(const struct sockaddr *sa1, const struct sockaddr *sa2,socklen_t salen)
{
if (sa1->sa_family != sa2->sa_family)
return(-1);
if(sa1->sa_family==AF_INET) {
return(memcmp( &((struct sockaddr_in *) sa1)->sin_addr,
&((struct sockaddr_in *) sa2)->sin_addr,
sizeof(struct in_addr)));
}
return (-1);
}
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