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mptcp: Create SUBFLOW socket for incoming connections
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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>
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@davem330
Peter Krystad authored and davem330 committed Jan 24, 2020
1 parent cec37a6 commit cf7da0d
Showing 1 changed file with 231 additions and 5 deletions.
236 changes: 231 additions & 5 deletions net/mptcp/protocol.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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"

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -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,
Expand All @@ -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);
Expand All @@ -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);
Expand All @@ -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)
{
Expand All @@ -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();

Expand Down Expand Up @@ -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)
Expand Down

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