sock_diag: specify info_size per inet protocol

Previously, there was no clear distinction between the inet protocols
that used struct tcp_info to report information and those that didn't.
This change adds a specific size attribute to the inet_diag_handler
struct which defines these interfaces.  This will make dispatching
sock_diag get_info requests identical for all inet protocols in a
following patch.

Tested: ss -au
Tested: ss -at
Signed-off-by: Craig Gallek <kraig@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 4d32262..b1f01174 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -200,9 +200,9 @@
 	}
 #undef EXPIRES_IN_MS
 
-	if (ext & (1 << (INET_DIAG_INFO - 1))) {
+	if ((ext & (1 << (INET_DIAG_INFO - 1))) && handler->idiag_info_size) {
 		attr = nla_reserve(skb, INET_DIAG_INFO,
-				   sizeof(struct tcp_info));
+				   handler->idiag_info_size);
 		if (!attr)
 			goto errout;