[PATCH] mptcp: Align mptcp_inet6_sk with other protocols

[Pedro Falcato <pfalcato@suse.de>]

Ever since commit f5f80e32de12 ("ipv6: remove hard coded limitation on
ipv6_pinfo") that protocols stopped using the old "obj_size -
sizeof(struct ipv6_pinfo)" way of grabbing ipv6_pinfo, that severely
restricted struct layout and caused fun, hard to see issues.

However, mptcp_inet6_sk wasn't fixed (unlike tcp_inet6_sk). Do so.
The non-cloned sockets already do the right thing using
ipv6_pinfo_offset + the generic IPv6 code.

Signed-off-by: Pedro Falcato <pfalcato@suse.de>
---
 net/mptcp/protocol.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 26ffa06c21e8..c4fd558307f2 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3142,9 +3142,9 @@ static int mptcp_disconnect(struct sock *sk, int flags)
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 static struct ipv6_pinfo *mptcp_inet6_sk(const struct sock *sk)
 {
-	unsigned int offset = sizeof(struct mptcp6_sock) - sizeof(struct ipv6_pinfo);
+	struct mptcp6_sock *msk6 = container_of(mptcp_sk(sk), struct mptcp6_sock, msk);
 
-	return (struct ipv6_pinfo *)(((u8 *)sk) + offset);
+	return &msk6->np;
 }
 
 static void mptcp_copy_ip6_options(struct sock *newsk, const struct sock *sk)
-- 
2.49.0