[PATCH 7/8] tcp: Protect init socket pools with mutex for thread safety

[Laurent Vivier <lvivier@redhat.com>]

The pre-opened socket pools init_sock_pool4/6 are consumed by
tcp_conn_pool_sock() when creating new connections from any worker
thread, and refilled by tcp_sock_refill_pool() from tcp_timer() in
post_handler(). These can run concurrently on different threads.

Add a mutex protecting both operations in tcp_conn_sock() and
tcp_sock_refill_init(), where init namespace pools are accessed.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 tcp.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/tcp.c b/tcp.c
index 955012355d69..019340c1c348 100644
--- a/tcp.c
+++ b/tcp.c
@@ -293,6 +293,7 @@
 #include <sys/uio.h>
 #include <time.h>
 #include <arpa/inet.h>
+#include <pthread.h>
 
 #include <linux/sockios.h>
 #include <linux/sock_diag.h>
@@ -439,6 +440,7 @@ static socklen_t tcp_info_size;
 /* Pools for pre-opened sockets (in init) */
 int init_sock_pool4		[TCP_SOCK_POOL_SIZE];
 int init_sock_pool6		[TCP_SOCK_POOL_SIZE];
+static pthread_mutex_t sock_pool_lock = PTHREAD_MUTEX_INITIALIZER;
 
 /**
  * conn_at_sidx() - Get TCP connection specific flow at given sidx
@@ -1568,7 +1570,11 @@ int tcp_conn_sock(sa_family_t af)
 	int *pool = af == AF_INET6 ? init_sock_pool6 : init_sock_pool4;
 	int s;
 
-	if ((s = tcp_conn_pool_sock(pool)) >= 0)
+	pthread_mutex_lock(&sock_pool_lock);
+	s = tcp_conn_pool_sock(pool);
+	pthread_mutex_unlock(&sock_pool_lock);
+
+	if (s >= 0)
 		return s;
 
 	/* If the pool is empty we just open a new one without refilling the
@@ -2857,6 +2863,7 @@ int tcp_sock_refill_pool(int pool[], sa_family_t af)
  */
 static void tcp_sock_refill_init(const struct ctx *c)
 {
+	pthread_mutex_lock(&sock_pool_lock);
 	if (c->ifi4) {
 		int rc = tcp_sock_refill_pool(init_sock_pool4, AF_INET);
 		if (rc < 0)
@@ -2869,6 +2876,7 @@ static void tcp_sock_refill_init(const struct ctx *c)
 			warn("TCP: Error refilling IPv6 host socket pool: %s",
 			     strerror_(-rc));
 	}
+	pthread_mutex_unlock(&sock_pool_lock);
 }
 
 /**
-- 
2.54.0