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 <vda.linux@googlemail.com>
diff --git a/networking/traceroute.c b/networking/traceroute.c
index 96f9d34..85181ab 100644
--- a/networking/traceroute.c
+++ b/networking/traceroute.c
@@ -398,18 +398,23 @@
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 @@
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 @@
static int
common_traceroute_main(int op, char **argv)
{
- int i;
int minpacket;
int tos = 0;
int max_ttl = 30;
@@ -973,6 +977,7 @@
#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 @@
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 @@
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 @@
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 @@
++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)