[PATCH net-next 3/3] mptcp: support IPV6_V6ONLY setsockopt

[Florian Westphal]

Without this, Opensshd fails to open an ipv6 socket listening
socket:
  error: setsockopt IPV6_V6ONLY: Operation not supported
  error: Bind to port 22 on :: failed: Address already in use.

Opensshd opens an ipv4 and and ipv6 listening socket, but because
IPV6_V6ONLY setsockopt fails, the port number is already in use.

Signed-off-by: Florian Westphal <f...@strlen.de>
---
 net/mptcp/protocol.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 612f6d49f1bb..3ab060e30038 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1632,6 +1632,33 @@ static int mptcp_setsockopt_sol_socket(struct mptcp_sock 
*msk, int optname,
        return sock_setsockopt(sk->sk_socket, SOL_SOCKET, optname, optval, 
optlen);
 }
 
+static int mptcp_setsockopt_v6(struct mptcp_sock *msk, int optname,
+                              char __user *optval, unsigned int optlen)
+{
+       struct sock *sk = (struct sock *)msk;
+       int ret = -EOPNOTSUPP;
+       struct socket *ssock;
+
+       switch (optname) {
+       case IPV6_V6ONLY:
+               lock_sock(sk);
+               ssock = __mptcp_nmpc_socket(msk);
+               if (!ssock) {
+                       release_sock(sk);
+                       return -EINVAL;
+               }
+
+               ret = tcp_setsockopt(ssock->sk, SOL_IPV6, optname, optval, 
optlen);
+               if (ret == 0)
+                       sk->sk_ipv6only = ssock->sk->sk_ipv6only;
+
+               release_sock(sk);
+               break;
+       }
+
+       return ret;
+}
+
 static int mptcp_setsockopt(struct sock *sk, int level, int optname,
                            char __user *optval, unsigned int optlen)
 {
@@ -1655,6 +1682,9 @@ static int mptcp_setsockopt(struct sock *sk, int level, 
int optname,
        if (ssk)
                return tcp_setsockopt(ssk, level, optname, optval, optlen);
 
+       if (level == SOL_IPV6)
+               return mptcp_setsockopt_v6(msk, optname, optval, optlen);
+
        return -EOPNOTSUPP;
 }
 
-- 
2.26.2