sock: support per-packet fwmark

index dfe2eb8..03ca20f 100644
@@ -1514,6 +1514,13 @@ void sock_kfree_s(struct sock *sk, void *mem, int size);
 void sock_kzfree_s(struct sock *sk, void *mem, int size);
 void sk_send_sigurg(struct sock *sk);
 
+struct sockcm_cookie {
+	u32 mark;
+};
+
+int sock_cmsg_send(struct sock *sk, struct msghdr *msg,
+		   struct sockcm_cookie *sockc);
+
 /*
  * Functions to fill in entries in struct proto_ops when a protocol
  * does not implement a particular function.

index 7dd1263..3395777 100644
@@ -1852,6 +1852,32 @@ struct sk_buff *sock_alloc_send_skb(struct sock *sk, unsigned long size,
 }
 EXPORT_SYMBOL(sock_alloc_send_skb);
 
+int sock_cmsg_send(struct sock *sk, struct msghdr *msg,
+		   struct sockcm_cookie *sockc)
+{
+	struct cmsghdr *cmsg;
+
+	for_each_cmsghdr(cmsg, msg) {
+		if (!CMSG_OK(msg, cmsg))
+			return -EINVAL;
+		if (cmsg->cmsg_level != SOL_SOCKET)
+			continue;
+		switch (cmsg->cmsg_type) {
+		case SO_MARK:
+			if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
+				return -EPERM;
+			if (cmsg->cmsg_len != CMSG_LEN(sizeof(u32)))
+				return -EINVAL;
+			sockc->mark = *(u32 *)CMSG_DATA(cmsg);
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+	return 0;
+}
+EXPORT_SYMBOL(sock_cmsg_send);
+
 /* On 32bit arches, an skb frag is limited to 2^15 */
 #define SKB_FRAG_PAGE_ORDER	get_order(32768)
 

index 81c900f..9d8c7fa 100644
@@ -2630,6 +2630,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 	__be16 proto;
 	unsigned char *addr;
 	int err, reserve = 0;
+	struct sockcm_cookie sockc;
 	struct virtio_net_hdr vnet_hdr = { 0 };
 	int offset = 0;
 	int vnet_hdr_len;

@@ -2665,6 +2666,13 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 	if (unlikely(!(dev->flags & IFF_UP)))
 		goto out_unlock;
 
+	sockc.mark = sk->sk_mark;
+	if (msg->msg_controllen) {
+		err = sock_cmsg_send(sk, msg, &sockc);
+		if (unlikely(err))
+			goto out_unlock;
+	}
+
 	if (sock->type == SOCK_RAW)
 		reserve = dev->hard_header_len;
 	if (po->has_vnet_hdr) {

@@ -2774,7 +2782,7 @@ static int packet_snd(struct socket *sock, struct msghdr *msg, size_t len)
 	skb->protocol = proto;
 	skb->dev = dev;
 	skb->priority = sk->sk_priority;
-	skb->mark = sk->sk_mark;
+	skb->mark = sockc.mark;
 
 	packet_pick_tx_queue(dev, skb);