sock: support per-packet fwmark

It's useful to allow users to set fwmark for an individual packet,
without changing the socket state. The function this patch adds in
sock layer can be used by the protocols that need such a feature.

Signed-off-by: Edward Hyunkoo Jee <edjee@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 0 deletions

diff --git a/net/core/sock.c b/net/core/sock.c
index 7dd1263e4c24..33957776cc1a 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -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)