tcp, netlink, HAS{BYTES_ACKED,MIN_RTT,GETRANDOM} and NETLINK_GET_STRICT_CHK

tcpi_bytes_acked and tcpi_min_rtt are only available on recent
kernel versions: provide fall-back paths (incurring some grade of
performance penalty).

Support for getrandom() was introduced in Linux 3.17 and glibc 2.25:
provide an alternate mechanism for that as well, reading from
/dev/random.

Also check if NETLINK_GET_STRICT_CHK is defined before using it:
it's not strictly needed, we'll filter out irrelevant results from
netlink anyway.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/netlink.c b/netlink.c
index 0948f45..3ba5f05 100644
--- a/netlink.c
+++ b/netlink.c
@@ -46,7 +46,10 @@ static int nl_seq;
 static int nl_sock_init_do(void *arg)
 {
 	struct sockaddr_nl addr = { .nl_family = AF_NETLINK, };
-	int *s = &nl_sock, v = 1;
+	int *s = &nl_sock;
+#ifdef NETLINK_GET_STRICT_CHK
+	int y = 1;
+#endif
 
 ns:
 	if (((*s) = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE)) < 0 ||
@@ -56,7 +59,9 @@ ns:
 	if (*s == -1 || !arg || s == &nl_sock_ns)
 		return 0;
 
-	setsockopt(*s, SOL_NETLINK, NETLINK_GET_STRICT_CHK, &v, sizeof(v));
+#ifdef NETLINK_GET_STRICT_CHK
+	setsockopt(*s, SOL_NETLINK, NETLINK_GET_STRICT_CHK, &y, sizeof(y));
+#endif
 
 	ns_enter((struct ctx *)arg);
 	s = &nl_sock_ns;