[PATCH v2] BUG/MINOR: tcp: don't try to set defaultmss when value is negative

[William Dauchy]

when `getsockopt` previously failed, we were trying to set defaultmss
with -2 value.

this is a followup of github issue #499

this should be backported to all versions >= v1.8

Fixes: 153659f1ae69a1 ("MINOR: tcp: When binding socket, attempt to
reuse one from the old proc.")
Signed-off-by: William Dauchy <w.dau...@criteo.com>
---
 src/proto_tcp.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index a9d5229c9..044ade430 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -906,9 +906,9 @@ int tcp_bind_listener(struct listener *listener, char 
*errmsg, int errlen)
                        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) {
+               if (defaultmss > 0 &&
+                   tmpmaxseg != defaultmss &&
+                   setsockopt(fd, IPPROTO_TCP, TCP_MAXSEG, &defaultmss, 
sizeof(defaultmss)) == -1) {
                        msg = "cannot set MSS";
                        err |= ERR_WARN;
                }
-- 
2.25.0