BUILD: make proto_tcp.c compatible with musl library
musl library expose tcp_info structure only when _GNU_SOURCE is defined.
This is required to build HAProxy on OSes relying musl such as Alpine
Linux.
diff --git a/src/proto_tcp.c b/src/proto_tcp.c
index 4f6b3c3..717ba28 100644
--- a/src/proto_tcp.c
+++ b/src/proto_tcp.c
@@ -10,6 +10,11 @@
*
*/
+/* this is to have tcp_info defined on systems using musl
+ * library, such as Alpine Linux
+ */
+#define _GNU_SOURCE
+
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>