sock_diag: implement a get_info handler for inet

This get_info handler will simply dispatch to the appropriate
existing inet protocol handler.

This patch also includes a new netlink attribute
(INET_DIAG_PROTOCOL).  This attribute is currently only used
for multicast messages.  Without this attribute, there is no
way of knowing the IP protocol used by the socket information
being broadcast.  This attribute is not necessary in the 'dump'
variant of this protocol (though it could easily be added)
because dump requests are issued for specific family/protocol
pairs.

Tested: ss -E (note, the -E option has not yet been merged into
the upstream version of ss).

Signed-off-by: Craig Gallek <kraig@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 65f791f..697b86d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2624,13 +2624,15 @@ EXPORT_SYMBOL(compat_tcp_setsockopt);
 /* Return information about state of tcp endpoint in API format. */
 void tcp_get_info(struct sock *sk, struct tcp_info *info)
 {
-	const struct tcp_sock *tp = tcp_sk(sk);
+	const struct tcp_sock *tp = tcp_sk(sk); /* iff sk_type == SOCK_STREAM */
 	const struct inet_connection_sock *icsk = inet_csk(sk);
 	u32 now = tcp_time_stamp;
 	unsigned int start;
 	u32 rate;
 
 	memset(info, 0, sizeof(*info));
+	if (sk->sk_type != SOCK_STREAM)
+		return;
 
 	info->tcpi_state = sk->sk_state;
 	info->tcpi_ca_state = icsk->icsk_ca_state;