mnl: mnl_set_rcvbuffer() skips buffer size update if it is too small

Check for existing buffer size, if this is larger than the newer buffer
size, skip this size update.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/mnl.c b/src/mnl.c
index 288a887d..859c7d77 100644
--- a/src/mnl.c
+++ b/src/mnl.c
@@ -233,10 +233,21 @@ static void mnl_set_sndbuffer(const struct mnl_socket *nl,
 	nlbuffsiz = newbuffsiz;
 }
 
+static unsigned int nlsndbufsiz;
+
 static int mnl_set_rcvbuffer(const struct mnl_socket *nl, size_t bufsiz)
 {
+	socklen_t len = sizeof(nlsndbufsiz);
 	int ret;
 
+	if (!nlsndbufsiz) {
+		getsockopt(mnl_socket_get_fd(nl), SOL_SOCKET, SO_RCVBUF,
+			   &nlsndbufsiz, &len);
+	}
+
+	if (nlsndbufsiz >= bufsiz)
+		return 0;
+
 	ret = setsockopt(mnl_socket_get_fd(nl), SOL_SOCKET, SO_RCVBUFFORCE,
 			 &bufsiz, sizeof(socklen_t));
 	if (ret < 0) {