mptcp: provide subflow aware release function

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
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/mptcp/protocol.c | 55 ++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 53 insertions(+), 2 deletions(-)

On Mon, 2021-02-15 at 16:36 +0100, Florian Westphal wrote:
> 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
> Signed-off-by: Florian Westphal <fw@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 19faa43be2f8..d811f60a867b 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>
> @@ -3388,10 +3390,34 @@ 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,
> @@ -3489,10 +3515,35 @@ 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,


Nice, LGTM. Thanks Florian!

/P

Hi Florian, Paolo,

On 15/02/2021 16:36, Florian Westphal wrote:
> 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
> Signed-off-by: Florian Westphal <fw@strlen.de>

Thank you for the patch and the review!

Just applied in our tree with Paolo's ACK:

- aee946a79980: mptcp: provide subflow aware release function
- Results: 1de5e73fbb6c..9344b5c5d36e

Tests + export are in progress!

Cheers,
Matt