net/smc: original socket family in inet_sock_diag

Commit ed75986f ("net/smc: ipv6 support for smc_diag.c") changed the
value of the diag_family field. The idea was to indicate the family of
the IP address in the inet_diag_sockid field. But the change makes it
impossible to distinguish an inet_sock_diag response message from SMC
sock_diag response. This patch restores the original behaviour and sends
AF_SMC as value of the diag_family field.

Fixes: ed75986f ("net/smc: ipv6 support for smc_diag.c")
Reported-by: Eugene Syromiatnikov <esyr@redhat.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/smc/smc_diag.c

@@ -38,6 +38,7 @@ static void smc_diag_msg_common_fill(struct smc_diag_msg *r, struct sock *sk)
 {
 	struct smc_sock *smc = smc_sk(sk);
 
+	r->diag_family = sk->sk_family;
 	if (!smc->clcsock)
 		return;
 	r->id.idiag_sport = htons(smc->clcsock->sk->sk_num);
@@ -45,14 +46,12 @@ static void smc_diag_msg_common_fill(struct smc_diag_msg *r, struct sock *sk)
 	r->id.idiag_if = smc->clcsock->sk->sk_bound_dev_if;
 	sock_diag_save_cookie(sk, r->id.idiag_cookie);
 	if (sk->sk_protocol == SMCPROTO_SMC) {
-		r->diag_family = PF_INET;
 		memset(&r->id.idiag_src, 0, sizeof(r->id.idiag_src));
 		memset(&r->id.idiag_dst, 0, sizeof(r->id.idiag_dst));
 		r->id.idiag_src[0] = smc->clcsock->sk->sk_rcv_saddr;
 		r->id.idiag_dst[0] = smc->clcsock->sk->sk_daddr;
 #if IS_ENABLED(CONFIG_IPV6)
 	} else if (sk->sk_protocol == SMCPROTO_SMC6) {
-		r->diag_family = PF_INET6;
 		memcpy(&r->id.idiag_src, &smc->clcsock->sk->sk_v6_rcv_saddr,
 		       sizeof(smc->clcsock->sk->sk_v6_rcv_saddr));
 		memcpy(&r->id.idiag_dst, &smc->clcsock->sk->sk_v6_daddr,