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Tcp keep-alive: send three probes before detectin an error.

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Otherwise we end with less reliable connections because it's too easy
that a single packet gets lost.
This commit is contained in:
antirez 2013-02-08 17:06:01 +01:00
parent 98b1a852b4
commit 76a5b21c3a
1 changed files with 8 additions and 4 deletions
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12
src/anet.c
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@ -100,15 +100,19 @@ int anetKeepAlive(char *err, int fd, int interval)
return ANET_ERR; return ANET_ERR;
} }
/* Send next probes after interval. */ /* Send next probes after the specified interval. Note that we set the
val = interval; * delay as interval / 3, as we send three probes before detecting
* an error (see the next setsockopt call). */
val = interval/3;
if (val == 0) val = 1;
if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPINTVL, &val, sizeof(val)) < 0) { if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPINTVL, &val, sizeof(val)) < 0) {
anetSetError(err, "setsockopt TCP_KEEPINTVL: %s\n", strerror(errno)); anetSetError(err, "setsockopt TCP_KEEPINTVL: %s\n", strerror(errno));
return ANET_ERR; return ANET_ERR;
} }
/* Consider the socket in error state after just one missing ACK reply. */ /* Consider the socket in error state after three we send three ACK
val = 1; * probes without getting a reply. */
val = 3;
if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPCNT, &val, sizeof(val)) < 0) { if (setsockopt(fd, IPPROTO_TCP, TCP_KEEPCNT, &val, sizeof(val)) < 0) {
anetSetError(err, "setsockopt TCP_KEEPCNT: %s\n", strerror(errno)); anetSetError(err, "setsockopt TCP_KEEPCNT: %s\n", strerror(errno));
return ANET_ERR; return ANET_ERR;