sock: add SOCK_ZEROCOPY sockopt
The send call ignores unknown flags. Legacy applications may already
unwittingly pass MSG_ZEROCOPY. Continue to ignore this flag unless a
socket opts in to zerocopy.
Introduce socket option SO_ZEROCOPY to enable MSG_ZEROCOPY processing.
Processes can also query this socket option to detect kernel support
for the feature. Older kernels will return ENOPROTOOPT.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/sock.c b/net/core/sock.c
index e8b6968..9ea988d 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1055,6 +1055,20 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
if (val == 1)
dst_negative_advice(sk);
break;
+
+ case SO_ZEROCOPY:
+ if (sk->sk_family != PF_INET && sk->sk_family != PF_INET6)
+ ret = -ENOTSUPP;
+ else if (sk->sk_protocol != IPPROTO_TCP)
+ ret = -ENOTSUPP;
+ else if (sk->sk_state != TCP_CLOSE)
+ ret = -EBUSY;
+ else if (val < 0 || val > 1)
+ ret = -EINVAL;
+ else
+ sock_valbool_flag(sk, SOCK_ZEROCOPY, valbool);
+ break;
+
default:
ret = -ENOPROTOOPT;
break;
@@ -1383,6 +1397,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
v.val64 = sock_gen_cookie(sk);
break;
+ case SO_ZEROCOPY:
+ v.val = sock_flag(sk, SOCK_ZEROCOPY);
+ break;
+
default:
/* We implement the SO_SNDLOWAT etc to not be settable
* (1003.1g 7).