mptcp: Create SUBFLOW socket for incoming connections

Add subflow_request_sock type that extends tcp_request_sock
and add an is_mptcp flag to tcp_request_sock distinguish them.

Override the listen() and accept() methods of the MPTCP
socket proto_ops so they may act on the subflow socket.

Override the conn_request() and syn_recv_sock() handlers
in the inet_connection_sock to handle incoming MPTCP
SYNs and the ACK to the response SYN.

Add handling in tcp_output.c to add MP_CAPABLE to an outgoing
SYN-ACK response for a subflow_request_sock.

Co-developed-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Co-developed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Co-developed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Peter Krystad <peter.krystad@linux.intel.com>
Signed-off-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index bdd58da1e4f6537aa6c3704c71c4dadd68c53df9..e08a25eabcd57693f234d7e02794792fad866e2f 100644 (file)
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -14,6 +14,9 @@
 #include <net/inet_hashtables.h>
 #include <net/protocol.h>
 #include <net/tcp.h>
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+#include <net/transp_v6.h>
+#endif
 #include <net/mptcp.h>
 #include "protocol.h"
 
@@ -212,6 +215,90 @@ static void mptcp_close(struct sock *sk, long timeout)
        sk_common_release(sk);
 }
 
+static void mptcp_copy_inaddrs(struct sock *msk, const struct sock *ssk)
+{
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+       const struct ipv6_pinfo *ssk6 = inet6_sk(ssk);
+       struct ipv6_pinfo *msk6 = inet6_sk(msk);
+
+       msk->sk_v6_daddr = ssk->sk_v6_daddr;
+       msk->sk_v6_rcv_saddr = ssk->sk_v6_rcv_saddr;
+
+       if (msk6 && ssk6) {
+               msk6->saddr = ssk6->saddr;
+               msk6->flow_label = ssk6->flow_label;
+       }
+#endif
+
+       inet_sk(msk)->inet_num = inet_sk(ssk)->inet_num;
+       inet_sk(msk)->inet_dport = inet_sk(ssk)->inet_dport;
+       inet_sk(msk)->inet_sport = inet_sk(ssk)->inet_sport;
+       inet_sk(msk)->inet_daddr = inet_sk(ssk)->inet_daddr;
+       inet_sk(msk)->inet_saddr = inet_sk(ssk)->inet_saddr;
+       inet_sk(msk)->inet_rcv_saddr = inet_sk(ssk)->inet_rcv_saddr;
+}
+
+static struct sock *mptcp_accept(struct sock *sk, int flags, int *err,
+                                bool kern)
+{
+       struct mptcp_sock *msk = mptcp_sk(sk);
+       struct socket *listener;
+       struct sock *newsk;
+
+       listener = __mptcp_nmpc_socket(msk);
+       if (WARN_ON_ONCE(!listener)) {
+               *err = -EINVAL;
+               return NULL;
+       }
+
+       pr_debug("msk=%p, listener=%p", msk, mptcp_subflow_ctx(listener->sk));
+       newsk = inet_csk_accept(listener->sk, flags, err, kern);
+       if (!newsk)
+               return NULL;
+
+       pr_debug("msk=%p, subflow is mptcp=%d", msk, sk_is_mptcp(newsk));
+
+       if (sk_is_mptcp(newsk)) {
+               struct mptcp_subflow_context *subflow;
+               struct sock *new_mptcp_sock;
+               struct sock *ssk = newsk;
+
+               subflow = mptcp_subflow_ctx(newsk);
+               lock_sock(sk);
+
+               local_bh_disable();
+               new_mptcp_sock = sk_clone_lock(sk, GFP_ATOMIC);
+               if (!new_mptcp_sock) {
+                       *err = -ENOBUFS;
+                       local_bh_enable();
+                       release_sock(sk);
+                       tcp_close(newsk, 0);
+                       return NULL;
+               }
+
+               mptcp_init_sock(new_mptcp_sock);
+
+               msk = mptcp_sk(new_mptcp_sock);
+               msk->remote_key = subflow->remote_key;
+               msk->local_key = subflow->local_key;
+               msk->subflow = NULL;
+
+               newsk = new_mptcp_sock;
+               mptcp_copy_inaddrs(newsk, ssk);
+               list_add(&subflow->node, &msk->conn_list);
+
+               /* will be fully established at mptcp_stream_accept()
+                * completion.
+                */
+               inet_sk_state_store(new_mptcp_sock, TCP_SYN_RECV);
+               bh_unlock_sock(new_mptcp_sock);
+               local_bh_enable();
+               release_sock(sk);
+       }
+
+       return newsk;
+}
+
 static int mptcp_get_port(struct sock *sk, unsigned short snum)
 {
        struct mptcp_sock *msk = mptcp_sk(sk);
@@ -246,12 +333,21 @@ void mptcp_finish_connect(struct sock *ssk)
        WRITE_ONCE(msk->local_key, subflow->local_key);
 }
 
+static void mptcp_sock_graft(struct sock *sk, struct socket *parent)
+{
+       write_lock_bh(&sk->sk_callback_lock);
+       rcu_assign_pointer(sk->sk_wq, &parent->wq);
+       sk_set_socket(sk, parent);
+       sk->sk_uid = SOCK_INODE(parent)->i_uid;
+       write_unlock_bh(&sk->sk_callback_lock);
+}
+
 static struct proto mptcp_prot = {
        .name           = "MPTCP",
        .owner          = THIS_MODULE,
        .init           = mptcp_init_sock,
        .close          = mptcp_close,
-       .accept         = inet_csk_accept,
+       .accept         = mptcp_accept,
        .shutdown       = tcp_shutdown,
        .sendmsg        = mptcp_sendmsg,
        .recvmsg        = mptcp_recvmsg,
@@ -266,10 +362,7 @@ static int mptcp_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
 {
        struct mptcp_sock *msk = mptcp_sk(sock->sk);
        struct socket *ssock;
-       int err = -ENOTSUPP;
-
-       if (uaddr->sa_family != AF_INET) // @@ allow only IPv4 for now
-               return err;
+       int err;
 
        lock_sock(sock->sk);
        ssock = __mptcp_socket_create(msk, MPTCP_SAME_STATE);
@@ -279,6 +372,8 @@ static int mptcp_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
        }
 
        err = ssock->ops->bind(ssock, uaddr, addr_len);
+       if (!err)
+               mptcp_copy_inaddrs(sock->sk, ssock->sk);
 
 unlock:
        release_sock(sock->sk);
@@ -299,14 +394,139 @@ static int mptcp_stream_connect(struct socket *sock, struct sockaddr *uaddr,
                goto unlock;
        }
 
+#ifdef CONFIG_TCP_MD5SIG
+       /* no MPTCP if MD5SIG is enabled on this socket or we may run out of
+        * TCP option space.
+        */
+       if (rcu_access_pointer(tcp_sk(ssock->sk)->md5sig_info))
+               mptcp_subflow_ctx(ssock->sk)->request_mptcp = 0;
+#endif
+
        err = ssock->ops->connect(ssock, uaddr, addr_len, flags);
        inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
+       mptcp_copy_inaddrs(sock->sk, ssock->sk);
 
 unlock:
        release_sock(sock->sk);
        return err;
 }
 
+static int mptcp_v4_getname(struct socket *sock, struct sockaddr *uaddr,
+                           int peer)
+{
+       if (sock->sk->sk_prot == &tcp_prot) {
+               /* we are being invoked from __sys_accept4, after
+                * mptcp_accept() has just accepted a non-mp-capable
+                * flow: sk is a tcp_sk, not an mptcp one.
+                *
+                * Hand the socket over to tcp so all further socket ops
+                * bypass mptcp.
+                */
+               sock->ops = &inet_stream_ops;
+       }
+
+       return inet_getname(sock, uaddr, peer);
+}
+
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+static int mptcp_v6_getname(struct socket *sock, struct sockaddr *uaddr,
+                           int peer)
+{
+       if (sock->sk->sk_prot == &tcpv6_prot) {
+               /* we are being invoked from __sys_accept4 after
+                * mptcp_accept() has accepted a non-mp-capable
+                * subflow: sk is a tcp_sk, not mptcp.
+                *
+                * Hand the socket over to tcp so all further
+                * socket ops bypass mptcp.
+                */
+               sock->ops = &inet6_stream_ops;
+       }
+
+       return inet6_getname(sock, uaddr, peer);
+}
+#endif
+
+static int mptcp_listen(struct socket *sock, int backlog)
+{
+       struct mptcp_sock *msk = mptcp_sk(sock->sk);
+       struct socket *ssock;
+       int err;
+
+       pr_debug("msk=%p", msk);
+
+       lock_sock(sock->sk);
+       ssock = __mptcp_socket_create(msk, TCP_LISTEN);
+       if (IS_ERR(ssock)) {
+               err = PTR_ERR(ssock);
+               goto unlock;
+       }
+
+       err = ssock->ops->listen(ssock, backlog);
+       inet_sk_state_store(sock->sk, inet_sk_state_load(ssock->sk));
+       if (!err)
+               mptcp_copy_inaddrs(sock->sk, ssock->sk);
+
+unlock:
+       release_sock(sock->sk);
+       return err;
+}
+
+static bool is_tcp_proto(const struct proto *p)
+{
+#if IS_ENABLED(CONFIG_MPTCP_IPV6)
+       return p == &tcp_prot || p == &tcpv6_prot;
+#else
+       return p == &tcp_prot;
+#endif
+}
+
+static int mptcp_stream_accept(struct socket *sock, struct socket *newsock,
+                              int flags, bool kern)
+{
+       struct mptcp_sock *msk = mptcp_sk(sock->sk);
+       struct socket *ssock;
+       int err;
+
+       pr_debug("msk=%p", msk);
+
+       lock_sock(sock->sk);
+       if (sock->sk->sk_state != TCP_LISTEN)
+               goto unlock_fail;
+
+       ssock = __mptcp_nmpc_socket(msk);
+       if (!ssock)
+               goto unlock_fail;
+
+       sock_hold(ssock->sk);
+       release_sock(sock->sk);
+
+       err = ssock->ops->accept(sock, newsock, flags, kern);
+       if (err == 0 && !is_tcp_proto(newsock->sk->sk_prot)) {
+               struct mptcp_sock *msk = mptcp_sk(newsock->sk);
+               struct mptcp_subflow_context *subflow;
+
+               /* set ssk->sk_socket of accept()ed flows to mptcp socket.
+                * This is needed so NOSPACE flag can be set from tcp stack.
+                */
+               list_for_each_entry(subflow, &msk->conn_list, node) {
+                       struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
+
+                       if (!ssk->sk_socket)
+                               mptcp_sock_graft(ssk, newsock);
+               }
+
+               inet_sk_state_store(newsock->sk, TCP_ESTABLISHED);
+       }
+
+       sock_put(ssock->sk);
+       return err;
+
+unlock_fail:
+       release_sock(sock->sk);
+       return -EINVAL;
+}
+
 static __poll_t mptcp_poll(struct file *file, struct socket *sock,
                           struct poll_table_struct *wait)
 {
@@ -332,6 +552,9 @@ void __init mptcp_init(void)
        mptcp_stream_ops.bind = mptcp_bind;
        mptcp_stream_ops.connect = mptcp_stream_connect;
        mptcp_stream_ops.poll = mptcp_poll;
+       mptcp_stream_ops.accept = mptcp_stream_accept;
+       mptcp_stream_ops.getname = mptcp_v4_getname;
+       mptcp_stream_ops.listen = mptcp_listen;
 
        mptcp_subflow_init();
 
@@ -371,6 +594,9 @@ int mptcpv6_init(void)
        mptcp_v6_stream_ops.bind = mptcp_bind;
        mptcp_v6_stream_ops.connect = mptcp_stream_connect;
        mptcp_v6_stream_ops.poll = mptcp_poll;
+       mptcp_v6_stream_ops.accept = mptcp_stream_accept;
+       mptcp_v6_stream_ops.getname = mptcp_v6_getname;
+       mptcp_v6_stream_ops.listen = mptcp_listen;
 
        err = inet6_register_protosw(&mptcp_v6_protosw);
        if (err)