[PATCH net 3/4] mptcp: provide subflow aware release function

[Paolo Abeni]

From: Florian Westphal <f...@strlen.de>

mptcp re-used inet(6)_release, so the subflow sockets are ignored.
Need to invoke ip(v6)_mc_drop_socket function to ensure mcast join
resources get free'd.

Fixes: 717e79c867ca5 ("mptcp: Add setsockopt()/getsockopt() socket operations")
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/110
Acked-by: Paolo Abeni <pab...@redhat.com>
Signed-off-by: Florian Westphal <f...@strlen.de>
---
 net/mptcp/protocol.c | 55 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 53 insertions(+), 2 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 78bd4bed07ac..0a6d12d2967d 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -11,6 +11,7 @@
 #include <linux/netdevice.h>
 #include <linux/sched/signal.h>
 #include <linux/atomic.h>
+#include <linux/igmp.h>
 #include <net/sock.h>
 #include <net/inet_common.h>
 #include <net/inet_hashtables.h>
@@ -19,6 +20,7 @@
 #include <net/tcp_states.h>
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 #include <net/transp_v6.h>
+#include <net/addrconf.h>
 #endif
 #include <net/mptcp.h>
 #include <net/xfrm.h>
@@ -3374,10 +3376,34 @@ static __poll_t mptcp_poll(struct file *file, struct 
socket *sock,
        return mask;
 }
 
+static int mptcp_release(struct socket *sock)
+{
+       struct mptcp_subflow_context *subflow;
+       struct sock *sk = sock->sk;
+       struct mptcp_sock *msk;
+
+       if (!sk)
+               return 0;
+
+       lock_sock(sk);
+
+       msk = mptcp_sk(sk);
+
+       mptcp_for_each_subflow(msk, subflow) {
+               struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+               ip_mc_drop_socket(ssk);
+       }
+
+       release_sock(sk);
+
+       return inet_release(sock);
+}
+
 static const struct proto_ops mptcp_stream_ops = {
        .family            = PF_INET,
        .owner             = THIS_MODULE,
-       .release           = inet_release,
+       .release           = mptcp_release,
        .bind              = mptcp_bind,
        .connect           = mptcp_stream_connect,
        .socketpair        = sock_no_socketpair,
@@ -3424,10 +3450,35 @@ void __init mptcp_proto_init(void)
 }
 
 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static int mptcp6_release(struct socket *sock)
+{
+       struct mptcp_subflow_context *subflow;
+       struct mptcp_sock *msk;
+       struct sock *sk = sock->sk;
+
+       if (!sk)
+               return 0;
+
+       lock_sock(sk);
+
+       msk = mptcp_sk(sk);
+
+       mptcp_for_each_subflow(msk, subflow) {
+               struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+               ip_mc_drop_socket(ssk);
+               ipv6_sock_mc_close(ssk);
+               ipv6_sock_ac_close(ssk);
+       }
+
+       release_sock(sk);
+       return inet6_release(sock);
+}
+
 static const struct proto_ops mptcp_v6_stream_ops = {
        .family            = PF_INET6,
        .owner             = THIS_MODULE,
-       .release           = inet6_release,
+       .release           = mptcp6_release,
        .bind              = mptcp_bind,
        .connect           = mptcp_stream_connect,
        .socketpair        = sock_no_socketpair,
-- 
2.26.2