[PATCH] selftest: net: Check return value from read

[Alessandro Zanni <alessandro.zanni87@gmail.com>]

Fix to retrieve the return value from the read() function
and raise an error if negative.

When building the test with the command
`make -C tools/testing/selftests TARGETS=net` emits the
following warning:

tfo.c: In function ‘run_server’:
tfo.c:84:9: warning: ignoring return value of ‘read’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   84 |         read(connfd, buf, 64);

Signed-off-by: Alessandro Zanni <alessandro.zanni87@gmail.com>
---
 tools/testing/selftests/net/tfo.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/tfo.c b/tools/testing/selftests/net/tfo.c
index eb3cac5e583c..8fce369e6c37 100644
--- a/tools/testing/selftests/net/tfo.c
+++ b/tools/testing/selftests/net/tfo.c
@@ -50,6 +50,7 @@ static void run_server(void)
 	socklen_t len;
 	char buf[64];
 	FILE *outfile;
+	int ret;
 
 	outfile = fopen(cfg_outfile, "w");
 	if (!outfile)
@@ -81,7 +82,9 @@ static void run_server(void)
 	if (getsockopt(connfd, SOL_SOCKET, SO_INCOMING_NAPI_ID, &opt, &len) < 0)
 		error(1, errno, "getsockopt(SO_INCOMING_NAPI_ID)");
 
-	read(connfd, buf, 64);
+	ret = read(connfd, buf, 64);
+	if (ret < 0)
+		error(1, errno, "read()");
 	fprintf(outfile, "%d\n", opt);
 
 	fclose(outfile);
-- 
2.43.0