From a348b4557d3d0af411135c23448a2c5a7cd82982 Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Thu, 5 May 2011 02:31:30 +0200 Subject: [PATCH] traceroute: properly reduce poll timeout 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 --- networking/traceroute.c | 61 +++++++++++++++++++++++++---------------- 1 file changed, 37 insertions(+), 24 deletions(-) diff --git a/networking/traceroute.c b/networking/traceroute.c index 96f9d3472..85181ab8d 100644 --- a/networking/traceroute.c +++ b/networking/traceroute.c @@ -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; @@ -730,7 +735,7 @@ packet_ok(int read_len, len_and_sockaddr *from_lsa, type, pr_type(type), icp->icmp6_code); read_len -= sizeof(struct icmp6_hdr); - for (i = 0; i < read_len ; i++) { + for (i = 0; i < read_len; i++) { if (i % 16 == 0) printf("%04x:", i); if (i % 4 == 0) @@ -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(); + + 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 */ - first = 0; - while ((read_len = wait_for_reply(from_lsa, to)) != 0) { - t2 = monotonic_us(); - i = packet_ok(read_len, from_lsa, to, seq); + 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) -- 2.25.1