[PATCH v2 2/5] tcp_splice: Check return value of setsockopt() for SO_RCVLOWAT

[Stefano Brivio <sbrivio@redhat.com>]

Spotted by Coverity, harmless as we would consider that successful
and check on the socket later from the timer, but printing a debug
message in that case is definitely wise, should it ever happen.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---
 tcp_splice.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/tcp_splice.c b/tcp_splice.c
index 5a406c6..f2d4fc6 100644
--- a/tcp_splice.c
+++ b/tcp_splice.c
@@ -598,11 +598,16 @@ eintr:
 			    readlen > (long)c->tcp.pipe_size / 10) {
 				int lowat = c->tcp.pipe_size / 4;
 
-				setsockopt(conn->s[fromside], SOL_SOCKET,
-					   SO_RCVLOWAT, &lowat, sizeof(lowat));
-
-				conn_flag(c, conn, lowat_set_flag);
-				conn_flag(c, conn, lowat_act_flag);
+				if (setsockopt(conn->s[fromside], SOL_SOCKET,
+					       SO_RCVLOWAT,
+					       &lowat, sizeof(lowat))) {
+					flow_trace(conn,
+						   "Setting SO_RCVLOWAT %i: %s",
+						   lowat, strerror(errno));
+				} else {
+					conn_flag(c, conn, lowat_set_flag);
+					conn_flag(c, conn, lowat_act_flag);
+				}
 			}
 
 			break;
-- 
@@ -598,11 +598,16 @@ eintr:
 			    readlen > (long)c->tcp.pipe_size / 10) {
 				int lowat = c->tcp.pipe_size / 4;
 
-				setsockopt(conn->s[fromside], SOL_SOCKET,
-					   SO_RCVLOWAT, &lowat, sizeof(lowat));
-
-				conn_flag(c, conn, lowat_set_flag);
-				conn_flag(c, conn, lowat_act_flag);
+				if (setsockopt(conn->s[fromside], SOL_SOCKET,
+					       SO_RCVLOWAT,
+					       &lowat, sizeof(lowat))) {
+					flow_trace(conn,
+						   "Setting SO_RCVLOWAT %i: %s",
+						   lowat, strerror(errno));
+				} else {
+					conn_flag(c, conn, lowat_set_flag);
+					conn_flag(c, conn, lowat_act_flag);
+				}
 			}
 
 			break;
-- 
2.43.0