sock: sockc cookie initializer

Initialize the cookie in one location to reduce code duplication and
avoid bugs from inconsistent initialization, such as that fixed in
commit 9887cba19978 ("ip: limit use of gso_size to udp").

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -1600,6 +1600,12 @@ struct sockcm_cookie {
 	u16 tsflags;
 };
 
+static inline void sockcm_init(struct sockcm_cookie *sockc,
+			       const struct sock *sk)
+{
+	*sockc = (struct sockcm_cookie) { .tsflags = sk->sk_tsflags };
+}
+
 int __sock_cmsg_send(struct sock *sk, struct msghdr *msg, struct cmsghdr *cmsg,
 		     struct sockcm_cookie *sockc);
 int sock_cmsg_send(struct sock *sk, struct msghdr *msg,

net/ipv4/tcp.c

@@ -1241,7 +1241,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 		/* 'common' sending to sendq */
 	}
 
-	sockc.tsflags = sk->sk_tsflags;
+	sockcm_init(&sockc, sk);
 	if (msg->msg_controllen) {
 		err = sock_cmsg_send(sk, msg, &sockc);
 		if (unlikely(err)) {

net/packet/af_packet.c

@@ -1951,8 +1951,7 @@ retry:
 		goto out_unlock;
 	}
 
-	sockc.transmit_time = 0;
-	sockc.tsflags = sk->sk_tsflags;
+	sockcm_init(&sockc, sk);
 	if (msg->msg_controllen) {
 		err = sock_cmsg_send(sk, msg, &sockc);
 		if (unlikely(err))
@@ -2636,8 +2635,7 @@ static int tpacket_snd(struct packet_sock *po, struct msghdr *msg)
 	if (unlikely(!(dev->flags & IFF_UP)))
 		goto out_put;
 
-	sockc.transmit_time = 0;
-	sockc.tsflags = po->sk.sk_tsflags;
+	sockcm_init(&sockc, &po->sk);
 	if (msg->msg_controllen) {
 		err = sock_cmsg_send(&po->sk, msg, &sockc);
 		if (unlikely(err))
@@ -2833,8 +2831,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 	if (unlikely(!(dev->flags & IFF_UP)))
 		goto out_unlock;
 
-	sockc.transmit_time = 0;
-	sockc.tsflags = sk->sk_tsflags;
+	sockcm_init(&sockc, sk);
 	sockc.mark = sk->sk_mark;
 	if (msg->msg_controllen) {
 		err = sock_cmsg_send(sk, msg, &sockc);