net: implement a SO_PROTOCOL getsockoption

Similar to SO_TYPE returning the socket type, SO_PROTOCOL allows to
retrieve the protocol used with a given socket.

I am not quite sure why we have that-many copies of socket.h, and why
the values are not the same on all arches either, but for where hex
numbers dominate, I use 0x1029 for SO_PROTOCOL as that seems to be
the next free unused number across a bunch of operating systems, or
so Google results make me want to believe. SO_PROTOCOL for others
just uses the next free Linux number, 38.

Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 0 deletions

diff --git a/net/core/sock.c b/net/core/sock.c
index a324a80c163e..ebce661234ac 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -482,6 +482,7 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
                 sk->sk_reuse = valbool;
                 break;
         case SO_TYPE:
+        case SO_PROTOCOL:
         case SO_ERROR:
                 ret = -ENOPROTOOPT;
                 break;
@@ -764,6 +765,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
                 v.val = sk->sk_type;
                 break;
 
+        case SO_PROTOCOL:
+                v.val = sk->sk_protocol;
+                break;
+
         case SO_ERROR:
                 v.val = -sock_error(sk);
                 if (v.val == 0)