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traceroute: properly reduce poll timeout

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This removes the problem where during the time we wait to declare
a target as unresponsive we receive an unrelated ICMP packet.
If there is enough traffic, this can make traceroute hang as
it never declares the target as unresponsive.

function                                             old     new   delta
common_traceroute_main                              4196    4261     +65

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2011-05-05 02:31:30 +02:00
parent d3e4be3ccb
commit a348b4557d
1 changed files with 37 additions and 24 deletions
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59
networking/traceroute.c
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@ -398,18 +398,23 @@ static len_and_sockaddr* dup_sockaddr(const len_and_sockaddr *lsa)
static int
wait_for_reply(len_and_sockaddr *from_lsa, struct sockaddr *to)
wait_for_reply(len_and_sockaddr *from_lsa, struct sockaddr *to, unsigned *timestamp_us, int *left_ms)
{
struct pollfd pfd[1];
int read_len = 0;
pfd[0].fd = rcvsock;
pfd[0].events = POLLIN;
if (safe_poll(pfd, 1, waittime * 1000) > 0) {
if (*left_ms >= 0 && safe_poll(pfd, 1, *left_ms) > 0) {
unsigned t;
read_len = recv_from_to(rcvsock,
recv_pkt, sizeof(recv_pkt),
/*flags:*/ 0,
/*flags:*/ MSG_DONTWAIT,
&from_lsa->u.sa, to, from_lsa->len);
t = monotonic_us();
*left_ms -= (t - *timestamp_us) / 1000;
*timestamp_us = t;
}
return read_len;
@ -819,7 +824,6 @@ print_delta_ms(unsigned t1p, unsigned t2p)
static int
common_traceroute_main(int op, char **argv)
{
int i;
int minpacket;
int tos = 0;
int max_ttl = 30;
@ -973,6 +977,7 @@ common_traceroute_main(int op, char **argv)
#if ENABLE_FEATURE_TRACEROUTE_SOURCE_ROUTE && defined IP_OPTIONS
if (lsrr > 0) {
unsigned char optlist[MAX_IPOPTLEN];
unsigned size;
/* final hop */
gwlist[lsrr] = dest_lsa->u.sin.sin_addr.s_addr;
@ -982,14 +987,14 @@ common_traceroute_main(int op, char **argv)
optlist[0] = IPOPT_NOP;
/* loose source route option */
optlist[1] = IPOPT_LSRR;
i = lsrr * sizeof(gwlist[0]);
optlist[2] = i + 3;
size = lsrr * sizeof(gwlist[0]);
optlist[2] = size + 3;
/* pointer to LSRR addresses */
optlist[3] = IPOPT_MINOFF;
memcpy(optlist + 4, gwlist, i);
memcpy(optlist + 4, gwlist, size);
if (setsockopt(sndsock, IPPROTO_IP, IP_OPTIONS,
(char *)optlist, i + sizeof(gwlist[0])) < 0) {
(char *)optlist, size + sizeof(gwlist[0])) < 0) {
bb_perror_msg_and_die("IP_OPTIONS");
}
}
@ -1103,28 +1108,34 @@ common_traceroute_main(int op, char **argv)
int unreachable = 0; /* counter */
int gotlastaddr = 0; /* flags */
int got_there = 0;
int first = 1;
printf("%2d", ttl);
for (probe = 0; probe < nprobes; ++probe) {
int read_len;
unsigned t1;
unsigned t2;
int left_ms;
struct ip *ip;
if (!first && pausemsecs > 0)
usleep(pausemsecs * 1000);
fflush_all();
if (probe != 0 && pausemsecs > 0)
usleep(pausemsecs * 1000);
t1 = monotonic_us();
send_probe(++seq, ttl);
t2 = t1 = monotonic_us();
first = 0;
while ((read_len = wait_for_reply(from_lsa, to)) != 0) {
t2 = monotonic_us();
i = packet_ok(read_len, from_lsa, to, seq);
left_ms = waittime * 1000;
while ((read_len = wait_for_reply(from_lsa, to, &t2, &left_ms)) != 0) {
int icmp_code;
/* Recv'ed a packet, or read error */
/* t2 = monotonic_us() - set by wait_for_reply */
if (read_len < 0)
continue;
icmp_code = packet_ok(read_len, from_lsa, to, seq);
/* Skip short packet */
if (i == 0)
if (icmp_code == 0)
continue;
if (!gotlastaddr
@ -1143,10 +1154,10 @@ common_traceroute_main(int op, char **argv)
printf(" (%d)", ip->ip_ttl);
/* time exceeded in transit */
if (i == -1)
if (icmp_code == -1)
break;
i--;
switch (i) {
icmp_code--;
switch (icmp_code) {
#if ENABLE_TRACEROUTE6
case ICMP6_DST_UNREACH_NOPORT << 8:
got_there = 1;
@ -1219,16 +1230,18 @@ common_traceroute_main(int op, char **argv)
++unreachable;
break;
default:
printf(" !<%d>", i);
printf(" !<%d>", icmp_code);
++unreachable;
break;
}
break;
}
} /* while (wait and read a packet) */
/* there was no packet at all? */
if (read_len == 0)
printf(" *");
}
} /* for (nprobes) */
bb_putchar('\n');
if (got_there
|| (unreachable > 0 && unreachable >= nprobes - 1)