Yet another patch, on top of the previous ones.
This one tries to get the default value of TCP_MAXSEG by creating a temporary
TCP socket, so that one can remove the "mss" entry from its configuration file,
and reset the mss value for any transferred socket from the old process.
Olivier
>From 7dc2432f3a7c4a9e9531adafa4524a199e394f90 Mon Sep 17 00:00:00 2001
From: Olivier Houchard <ohouch...@haproxy.com>
Date: Wed, 12 Apr 2017 19:32:15 +0200
Subject: [PATCH 10/10] MINOR: tcp: Attempt to reset TCP_MAXSEG when reusing a
socket.
Guess the default value for TCP_MAXSEG by binding a temporary TCP socket and
getting it, and use that in case the we're reusing a socket from the old
process, and its TCP_MAXSEG is different. That way one can reset the
TCP_MAXSEG value to the default one when reusing sockets.
---
src/proto_tcp.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 52 insertions(+), 3 deletions(-)
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index ea6b8f7..8050f3e 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -110,6 +110,12 @@ static struct protocol proto_tcpv6 = {
.nb_listeners = 0,
};
+/* Default TCP parameters, got by opening a temporary TCP socket. */
+#ifdef TCP_MAXSEG
+static int default_tcp_maxseg = -1;
+static int default_tcp6_maxseg = -1;
+#endif
+
/* Binds ipv4/ipv6 address <local> to socket <fd>, unless <flags> is set, in
which
* case we try to bind <remote>. <flags> is a 2-bit field consisting of :
* - 0 : ignore remote address (may even be a NULL pointer)
@@ -829,6 +835,35 @@ int tcp_bind_listener(struct listener *listener, char
*errmsg, int errlen)
int ext, ready;
socklen_t ready_len;
const char *msg = NULL;
+#ifdef TCP_MAXSEG
+
+ /* Create a temporary TCP socket to get default parameters we can't
+ * guess.
+ * */
+ ready_len = sizeof(default_tcp_maxseg);
+ if (default_tcp_maxseg == -1) {
+ default_tcp_maxseg = -2;
+ fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+ if (fd < 0)
+ Warning("Failed to create a temporary socket!\n");
+ else {
+ if (getsockopt(fd, IPPROTO_TCP, TCP_MAXSEG,
&default_tcp_maxseg,
+ &ready_len) == -1)
+ Warning("Failed to get the default value of
TCP_MAXSEG\n");
+ }
+ }
+ if (default_tcp6_maxseg == -1) {
+ default_tcp6_maxseg = -2;
+ fd = socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP);
+ if (fd >= 0) {
+ if (getsockopt(fd, IPPROTO_TCP, TCP_MAXSEG,
&default_tcp6_maxseg,
+ &ready_len) == -1)
+ Warning("Failed ot get the default value of
TCP_MAXSEG for IPv6\n");
+ close(fd);
+ }
+ }
+#endif
+
/* ensure we never return garbage */
if (errlen)
@@ -960,10 +995,24 @@ int tcp_bind_listener(struct listener *listener, char
*errmsg, int errlen)
msg = "cannot set MSS";
err |= ERR_WARN;
}
+ } else if (ext) {
+ int tmpmaxseg = -1;
+ int defaultmss;
+ socklen_t len = sizeof(tmpmaxseg);
+
+ if (listener->addr.ss_family == AF_INET)
+ defaultmss = default_tcp_maxseg;
+ else
+ defaultmss = default_tcp6_maxseg;
+
+ getsockopt(fd, IPPROTO_TCP, TCP_MAXSEG, &tmpmaxseg, &len);
+ if (tmpmaxseg != defaultmss &&
+ setsockopt(fd, IPPROTO_TCP, TCP_MAXSEG,
+ &defaultmss, sizeof(defaultmss)) == -1) {
+ msg = "cannot set MSS";
+ err |= ERR_WARN;
+ }
}
- /* XXX: No else, the way to get the default MSS will vary from system
- * to system.
- */
#endif
#if defined(TCP_USER_TIMEOUT)
if (listener->tcp_ut) {
--
2.9.3
