[PATCH] enable SO_KEEPALIVE for connected TCP sockets

[Eric Wong <normalperson@yhbt.net>]

Sockets may never receive notification of some link errors,
causing "git fetch" or similar processes to hang forever.
Enabling keepalive messages allows hung processes to error out
after a few minutes/hours depending on the keepalive settings of
the system.

This is a problem noticed when running non-interactive
cronjobs to mirror repositories using "git fetch".

Signed-off-by: Eric Wong <normalperson@yhbt.net>
---
 connect.c |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/connect.c b/connect.c
index 51990fa..d0f59ef 100644
--- a/connect.c
+++ b/connect.c
@@ -175,6 +175,15 @@ static void get_host_and_port(char **host, const char **port)
 	}
 }
 
+static void enable_keepalive(int sockfd)
+{
+	int ka = 1;
+
+	if (setsockopt(sockfd, SOL_SOCKET, SO_KEEPALIVE, &ka, sizeof(ka)) < 0)
+		fprintf(stderr, "unable to set SO_KEEPALIVE on socket: %s\n",
+			strerror(errno));
+}
+
 #ifndef NO_IPV6
 
 static const char *ai_name(const struct addrinfo *ai)
@@ -239,6 +248,8 @@ static int git_tcp_connect_sock(char *host, int flags)
 	if (sockfd < 0)
 		die("unable to connect to %s:\n%s", host, error_message.buf);
 
+	enable_keepalive(sockfd);
+
 	if (flags & CONNECT_VERBOSE)
 		fprintf(stderr, "done.\n");
 
@@ -312,6 +323,8 @@ static int git_tcp_connect_sock(char *host, int flags)
 	if (sockfd < 0)
 		die("unable to connect to %s:\n%s", host, error_message.buf);
 
+	enable_keepalive(sockfd);
+
 	if (flags & CONNECT_VERBOSE)
 		fprintf(stderr, "done.\n");
 
-- 
Eric Wong