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subflow.c
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// SPDX-License-Identifier: GPL-2.0
/* Multipath TCP
*
* Copyright (c) 2017 - 2019, Intel Corporation.
*/
#define pr_fmt(fmt) "MPTCP: " fmt
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <crypto/algapi.h>
#include <crypto/sha2.h>
#include <net/sock.h>
#include <net/inet_common.h>
#include <net/inet_hashtables.h>
#include <net/protocol.h>
#include <net/tcp.h>
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
#include <net/ip6_route.h>
#include <net/transp_v6.h>
#endif
#include <net/mptcp.h>
#include <uapi/linux/mptcp.h>
#include "protocol.h"
#include "mib.h"
#include <trace/events/mptcp.h>
static void mptcp_subflow_ops_undo_override(struct sock *ssk);
static void SUBFLOW_REQ_INC_STATS(struct request_sock *req,
enum linux_mptcp_mib_field field)
{
MPTCP_INC_STATS(sock_net(req_to_sk(req)), field);
}
static void subflow_req_destructor(struct request_sock *req)
{
struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
pr_debug("subflow_req=%p", subflow_req);
if (subflow_req->msk)
sock_put((struct sock *)subflow_req->msk);
mptcp_token_destroy_request(req);
tcp_request_sock_ops.destructor(req);
}
static void subflow_generate_hmac(u64 key1, u64 key2, u32 nonce1, u32 nonce2,
void *hmac)
{
u8 msg[8];
put_unaligned_be32(nonce1, &msg[0]);
put_unaligned_be32(nonce2, &msg[4]);
mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac);
}
static bool mptcp_can_accept_new_subflow(const struct mptcp_sock *msk)
{
return mptcp_is_fully_established((void *)msk) &&
((mptcp_pm_is_userspace(msk) &&
mptcp_userspace_pm_active(msk)) ||
READ_ONCE(msk->pm.accept_subflow));
}
/* validate received token and create truncated hmac and nonce for SYN-ACK */
static void subflow_req_create_thmac(struct mptcp_subflow_request_sock *subflow_req)
{
struct mptcp_sock *msk = subflow_req->msk;
u8 hmac[SHA256_DIGEST_SIZE];
get_random_bytes(&subflow_req->local_nonce, sizeof(u32));
subflow_generate_hmac(msk->local_key, msk->remote_key,
subflow_req->local_nonce,
subflow_req->remote_nonce, hmac);
subflow_req->thmac = get_unaligned_be64(hmac);
}
static struct mptcp_sock *subflow_token_join_request(struct request_sock *req)
{
struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
struct mptcp_sock *msk;
int local_id;
msk = mptcp_token_get_sock(sock_net(req_to_sk(req)), subflow_req->token);
if (!msk) {
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINNOTOKEN);
return NULL;
}
local_id = mptcp_pm_get_local_id(msk, (struct sock_common *)req);
if (local_id < 0) {
sock_put((struct sock *)msk);
return NULL;
}
subflow_req->local_id = local_id;
return msk;
}
static void subflow_init_req(struct request_sock *req, const struct sock *sk_listener)
{
struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
subflow_req->mp_capable = 0;
subflow_req->mp_join = 0;
subflow_req->csum_reqd = mptcp_is_checksum_enabled(sock_net(sk_listener));
subflow_req->allow_join_id0 = mptcp_allow_join_id0(sock_net(sk_listener));
subflow_req->msk = NULL;
mptcp_token_init_request(req);
}
static bool subflow_use_different_sport(struct mptcp_sock *msk, const struct sock *sk)
{
return inet_sk(sk)->inet_sport != inet_sk((struct sock *)msk)->inet_sport;
}
static void subflow_add_reset_reason(struct sk_buff *skb, u8 reason)
{
struct mptcp_ext *mpext = skb_ext_add(skb, SKB_EXT_MPTCP);
if (mpext) {
memset(mpext, 0, sizeof(*mpext));
mpext->reset_reason = reason;
}
}
/* Init mptcp request socket.
*
* Returns an error code if a JOIN has failed and a TCP reset
* should be sent.
*/
static int subflow_check_req(struct request_sock *req,
const struct sock *sk_listener,
struct sk_buff *skb)
{
struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
struct mptcp_options_received mp_opt;
bool opt_mp_capable, opt_mp_join;
pr_debug("subflow_req=%p, listener=%p", subflow_req, listener);
#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(sk_listener)->md5sig_info))
return -EINVAL;
#endif
mptcp_get_options(skb, &mp_opt);
opt_mp_capable = !!(mp_opt.suboptions & OPTIONS_MPTCP_MPC);
opt_mp_join = !!(mp_opt.suboptions & OPTIONS_MPTCP_MPJ);
if (opt_mp_capable) {
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MPCAPABLEPASSIVE);
if (opt_mp_join)
return 0;
} else if (opt_mp_join) {
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINSYNRX);
}
if (opt_mp_capable && listener->request_mptcp) {
int err, retries = MPTCP_TOKEN_MAX_RETRIES;
subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
again:
do {
get_random_bytes(&subflow_req->local_key, sizeof(subflow_req->local_key));
} while (subflow_req->local_key == 0);
if (unlikely(req->syncookie)) {
mptcp_crypto_key_sha(subflow_req->local_key,
&subflow_req->token,
&subflow_req->idsn);
if (mptcp_token_exists(subflow_req->token)) {
if (retries-- > 0)
goto again;
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
} else {
subflow_req->mp_capable = 1;
}
return 0;
}
err = mptcp_token_new_request(req);
if (err == 0)
subflow_req->mp_capable = 1;
else if (retries-- > 0)
goto again;
else
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_TOKENFALLBACKINIT);
} else if (opt_mp_join && listener->request_mptcp) {
subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq;
subflow_req->mp_join = 1;
subflow_req->backup = mp_opt.backup;
subflow_req->remote_id = mp_opt.join_id;
subflow_req->token = mp_opt.token;
subflow_req->remote_nonce = mp_opt.nonce;
subflow_req->msk = subflow_token_join_request(req);
/* Can't fall back to TCP in this case. */
if (!subflow_req->msk) {
subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
return -EPERM;
}
if (subflow_use_different_sport(subflow_req->msk, sk_listener)) {
pr_debug("syn inet_sport=%d %d",
ntohs(inet_sk(sk_listener)->inet_sport),
ntohs(inet_sk((struct sock *)subflow_req->msk)->inet_sport));
if (!mptcp_pm_sport_in_anno_list(subflow_req->msk, sk_listener)) {
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTSYNRX);
return -EPERM;
}
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTSYNRX);
}
subflow_req_create_thmac(subflow_req);
if (unlikely(req->syncookie)) {
if (mptcp_can_accept_new_subflow(subflow_req->msk))
subflow_init_req_cookie_join_save(subflow_req, skb);
else
return -EPERM;
}
pr_debug("token=%u, remote_nonce=%u msk=%p", subflow_req->token,
subflow_req->remote_nonce, subflow_req->msk);
}
return 0;
}
int mptcp_subflow_init_cookie_req(struct request_sock *req,
const struct sock *sk_listener,
struct sk_buff *skb)
{
struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk_listener);
struct mptcp_subflow_request_sock *subflow_req = mptcp_subflow_rsk(req);
struct mptcp_options_received mp_opt;
bool opt_mp_capable, opt_mp_join;
int err;
subflow_init_req(req, sk_listener);
mptcp_get_options(skb, &mp_opt);
opt_mp_capable = !!(mp_opt.suboptions & OPTIONS_MPTCP_MPC);
opt_mp_join = !!(mp_opt.suboptions & OPTIONS_MPTCP_MPJ);
if (opt_mp_capable && opt_mp_join)
return -EINVAL;
if (opt_mp_capable && listener->request_mptcp) {
if (mp_opt.sndr_key == 0)
return -EINVAL;
subflow_req->local_key = mp_opt.rcvr_key;
err = mptcp_token_new_request(req);
if (err)
return err;
subflow_req->mp_capable = 1;
subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
} else if (opt_mp_join && listener->request_mptcp) {
if (!mptcp_token_join_cookie_init_state(subflow_req, skb))
return -EINVAL;
subflow_req->mp_join = 1;
subflow_req->ssn_offset = TCP_SKB_CB(skb)->seq - 1;
}
return 0;
}
EXPORT_SYMBOL_GPL(mptcp_subflow_init_cookie_req);
static struct dst_entry *subflow_v4_route_req(const struct sock *sk,
struct sk_buff *skb,
struct flowi *fl,
struct request_sock *req)
{
struct dst_entry *dst;
int err;
tcp_rsk(req)->is_mptcp = 1;
subflow_init_req(req, sk);
dst = tcp_request_sock_ipv4_ops.route_req(sk, skb, fl, req);
if (!dst)
return NULL;
err = subflow_check_req(req, sk, skb);
if (err == 0)
return dst;
dst_release(dst);
if (!req->syncookie)
tcp_request_sock_ops.send_reset(sk, skb);
return NULL;
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
static struct dst_entry *subflow_v6_route_req(const struct sock *sk,
struct sk_buff *skb,
struct flowi *fl,
struct request_sock *req)
{
struct dst_entry *dst;
int err;
tcp_rsk(req)->is_mptcp = 1;
subflow_init_req(req, sk);
dst = tcp_request_sock_ipv6_ops.route_req(sk, skb, fl, req);
if (!dst)
return NULL;
err = subflow_check_req(req, sk, skb);
if (err == 0)
return dst;
dst_release(dst);
if (!req->syncookie)
tcp6_request_sock_ops.send_reset(sk, skb);
return NULL;
}
#endif
/* validate received truncated hmac and create hmac for third ACK */
static bool subflow_thmac_valid(struct mptcp_subflow_context *subflow)
{
u8 hmac[SHA256_DIGEST_SIZE];
u64 thmac;
subflow_generate_hmac(subflow->remote_key, subflow->local_key,
subflow->remote_nonce, subflow->local_nonce,
hmac);
thmac = get_unaligned_be64(hmac);
pr_debug("subflow=%p, token=%u, thmac=%llu, subflow->thmac=%llu\n",
subflow, subflow->token, thmac, subflow->thmac);
return thmac == subflow->thmac;
}
void mptcp_subflow_reset(struct sock *ssk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
struct sock *sk = subflow->conn;
/* must hold: tcp_done() could drop last reference on parent */
sock_hold(sk);
tcp_set_state(ssk, TCP_CLOSE);
tcp_send_active_reset(ssk, GFP_ATOMIC);
tcp_done(ssk);
if (!test_and_set_bit(MPTCP_WORK_CLOSE_SUBFLOW, &mptcp_sk(sk)->flags) &&
schedule_work(&mptcp_sk(sk)->work))
return; /* worker will put sk for us */
sock_put(sk);
}
static bool subflow_use_different_dport(struct mptcp_sock *msk, const struct sock *sk)
{
return inet_sk(sk)->inet_dport != inet_sk((struct sock *)msk)->inet_dport;
}
void __mptcp_set_connected(struct sock *sk)
{
if (sk->sk_state == TCP_SYN_SENT) {
inet_sk_state_store(sk, TCP_ESTABLISHED);
sk->sk_state_change(sk);
}
}
static void mptcp_set_connected(struct sock *sk)
{
mptcp_data_lock(sk);
if (!sock_owned_by_user(sk))
__mptcp_set_connected(sk);
else
__set_bit(MPTCP_CONNECTED, &mptcp_sk(sk)->cb_flags);
mptcp_data_unlock(sk);
}
static void subflow_finish_connect(struct sock *sk, const struct sk_buff *skb)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
struct mptcp_options_received mp_opt;
struct sock *parent = subflow->conn;
subflow->icsk_af_ops->sk_rx_dst_set(sk, skb);
/* be sure no special action on any packet other than syn-ack */
if (subflow->conn_finished)
return;
mptcp_propagate_sndbuf(parent, sk);
subflow->rel_write_seq = 1;
subflow->conn_finished = 1;
subflow->ssn_offset = TCP_SKB_CB(skb)->seq;
pr_debug("subflow=%p synack seq=%x", subflow, subflow->ssn_offset);
mptcp_get_options(skb, &mp_opt);
if (subflow->request_mptcp) {
if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPC)) {
MPTCP_INC_STATS(sock_net(sk),
MPTCP_MIB_MPCAPABLEACTIVEFALLBACK);
mptcp_do_fallback(sk);
pr_fallback(mptcp_sk(subflow->conn));
goto fallback;
}
if (mp_opt.suboptions & OPTION_MPTCP_CSUMREQD)
WRITE_ONCE(mptcp_sk(parent)->csum_enabled, true);
if (mp_opt.deny_join_id0)
WRITE_ONCE(mptcp_sk(parent)->pm.remote_deny_join_id0, true);
subflow->mp_capable = 1;
subflow->can_ack = 1;
subflow->remote_key = mp_opt.sndr_key;
pr_debug("subflow=%p, remote_key=%llu", subflow,
subflow->remote_key);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_MPCAPABLEACTIVEACK);
mptcp_finish_connect(sk);
mptcp_set_connected(parent);
} else if (subflow->request_join) {
u8 hmac[SHA256_DIGEST_SIZE];
if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPJ)) {
subflow->reset_reason = MPTCP_RST_EMPTCP;
goto do_reset;
}
subflow->backup = mp_opt.backup;
subflow->thmac = mp_opt.thmac;
subflow->remote_nonce = mp_opt.nonce;
subflow->remote_id = mp_opt.join_id;
pr_debug("subflow=%p, thmac=%llu, remote_nonce=%u backup=%d",
subflow, subflow->thmac, subflow->remote_nonce,
subflow->backup);
if (!subflow_thmac_valid(subflow)) {
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINACKMAC);
subflow->reset_reason = MPTCP_RST_EMPTCP;
goto do_reset;
}
if (!mptcp_finish_join(sk))
goto do_reset;
subflow_generate_hmac(subflow->local_key, subflow->remote_key,
subflow->local_nonce,
subflow->remote_nonce,
hmac);
memcpy(subflow->hmac, hmac, MPTCPOPT_HMAC_LEN);
subflow->mp_join = 1;
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINSYNACKRX);
if (subflow_use_different_dport(mptcp_sk(parent), sk)) {
pr_debug("synack inet_dport=%d %d",
ntohs(inet_sk(sk)->inet_dport),
ntohs(inet_sk(parent)->inet_dport));
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_JOINPORTSYNACKRX);
}
} else if (mptcp_check_fallback(sk)) {
fallback:
mptcp_rcv_space_init(mptcp_sk(parent), sk);
mptcp_set_connected(parent);
}
return;
do_reset:
subflow->reset_transient = 0;
mptcp_subflow_reset(sk);
}
static void subflow_set_local_id(struct mptcp_subflow_context *subflow, int local_id)
{
subflow->local_id = local_id;
subflow->local_id_valid = 1;
}
static int subflow_chk_local_id(struct sock *sk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
int err;
if (likely(subflow->local_id_valid))
return 0;
err = mptcp_pm_get_local_id(msk, (struct sock_common *)sk);
if (err < 0)
return err;
subflow_set_local_id(subflow, err);
return 0;
}
static int subflow_rebuild_header(struct sock *sk)
{
int err = subflow_chk_local_id(sk);
if (unlikely(err < 0))
return err;
return inet_sk_rebuild_header(sk);
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
static int subflow_v6_rebuild_header(struct sock *sk)
{
int err = subflow_chk_local_id(sk);
if (unlikely(err < 0))
return err;
return inet6_sk_rebuild_header(sk);
}
#endif
struct request_sock_ops mptcp_subflow_request_sock_ops;
static struct tcp_request_sock_ops subflow_request_sock_ipv4_ops __ro_after_init;
static int subflow_v4_conn_request(struct sock *sk, struct sk_buff *skb)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
pr_debug("subflow=%p", subflow);
/* Never answer to SYNs sent to broadcast or multicast */
if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
goto drop;
return tcp_conn_request(&mptcp_subflow_request_sock_ops,
&subflow_request_sock_ipv4_ops,
sk, skb);
drop:
tcp_listendrop(sk);
return 0;
}
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
static struct tcp_request_sock_ops subflow_request_sock_ipv6_ops __ro_after_init;
static struct inet_connection_sock_af_ops subflow_v6_specific __ro_after_init;
static struct inet_connection_sock_af_ops subflow_v6m_specific __ro_after_init;
static struct proto tcpv6_prot_override;
static int subflow_v6_conn_request(struct sock *sk, struct sk_buff *skb)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(sk);
pr_debug("subflow=%p", subflow);
if (skb->protocol == htons(ETH_P_IP))
return subflow_v4_conn_request(sk, skb);
if (!ipv6_unicast_destination(skb))
goto drop;
if (ipv6_addr_v4mapped(&ipv6_hdr(skb)->saddr)) {
__IP6_INC_STATS(sock_net(sk), NULL, IPSTATS_MIB_INHDRERRORS);
return 0;
}
return tcp_conn_request(&mptcp_subflow_request_sock_ops,
&subflow_request_sock_ipv6_ops, sk, skb);
drop:
tcp_listendrop(sk);
return 0; /* don't send reset */
}
#endif
/* validate hmac received in third ACK */
static bool subflow_hmac_valid(const struct request_sock *req,
const struct mptcp_options_received *mp_opt)
{
const struct mptcp_subflow_request_sock *subflow_req;
u8 hmac[SHA256_DIGEST_SIZE];
struct mptcp_sock *msk;
subflow_req = mptcp_subflow_rsk(req);
msk = subflow_req->msk;
if (!msk)
return false;
subflow_generate_hmac(msk->remote_key, msk->local_key,
subflow_req->remote_nonce,
subflow_req->local_nonce, hmac);
return !crypto_memneq(hmac, mp_opt->hmac, MPTCPOPT_HMAC_LEN);
}
static void mptcp_sock_destruct(struct sock *sk)
{
/* if new mptcp socket isn't accepted, it is free'd
* from the tcp listener sockets request queue, linked
* from req->sk. The tcp socket is released.
* This calls the ULP release function which will
* also remove the mptcp socket, via
* sock_put(ctx->conn).
*
* Problem is that the mptcp socket will be in
* ESTABLISHED state and will not have the SOCK_DEAD flag.
* Both result in warnings from inet_sock_destruct.
*/
if ((1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) {
sk->sk_state = TCP_CLOSE;
WARN_ON_ONCE(sk->sk_socket);
sock_orphan(sk);
}
mptcp_destroy_common(mptcp_sk(sk));
inet_sock_destruct(sk);
}
static void mptcp_force_close(struct sock *sk)
{
/* the msk is not yet exposed to user-space */
inet_sk_state_store(sk, TCP_CLOSE);
sk_common_release(sk);
}
static void subflow_ulp_fallback(struct sock *sk,
struct mptcp_subflow_context *old_ctx)
{
struct inet_connection_sock *icsk = inet_csk(sk);
mptcp_subflow_tcp_fallback(sk, old_ctx);
icsk->icsk_ulp_ops = NULL;
rcu_assign_pointer(icsk->icsk_ulp_data, NULL);
tcp_sk(sk)->is_mptcp = 0;
mptcp_subflow_ops_undo_override(sk);
}
static void subflow_drop_ctx(struct sock *ssk)
{
struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(ssk);
if (!ctx)
return;
subflow_ulp_fallback(ssk, ctx);
if (ctx->conn)
sock_put(ctx->conn);
kfree_rcu(ctx, rcu);
}
void mptcp_subflow_fully_established(struct mptcp_subflow_context *subflow,
struct mptcp_options_received *mp_opt)
{
struct mptcp_sock *msk = mptcp_sk(subflow->conn);
subflow->remote_key = mp_opt->sndr_key;
subflow->fully_established = 1;
subflow->can_ack = 1;
WRITE_ONCE(msk->fully_established, true);
}
static struct sock *subflow_syn_recv_sock(const struct sock *sk,
struct sk_buff *skb,
struct request_sock *req,
struct dst_entry *dst,
struct request_sock *req_unhash,
bool *own_req)
{
struct mptcp_subflow_context *listener = mptcp_subflow_ctx(sk);
struct mptcp_subflow_request_sock *subflow_req;
struct mptcp_options_received mp_opt;
bool fallback, fallback_is_fatal;
struct sock *new_msk = NULL;
struct sock *child;
pr_debug("listener=%p, req=%p, conn=%p", listener, req, listener->conn);
/* After child creation we must look for MPC even when options
* are not parsed
*/
mp_opt.suboptions = 0;
/* hopefully temporary handling for MP_JOIN+syncookie */
subflow_req = mptcp_subflow_rsk(req);
fallback_is_fatal = tcp_rsk(req)->is_mptcp && subflow_req->mp_join;
fallback = !tcp_rsk(req)->is_mptcp;
if (fallback)
goto create_child;
/* if the sk is MP_CAPABLE, we try to fetch the client key */
if (subflow_req->mp_capable) {
/* we can receive and accept an in-window, out-of-order pkt,
* which may not carry the MP_CAPABLE opt even on mptcp enabled
* paths: always try to extract the peer key, and fallback
* for packets missing it.
* Even OoO DSS packets coming legitly after dropped or
* reordered MPC will cause fallback, but we don't have other
* options.
*/
mptcp_get_options(skb, &mp_opt);
if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPC)) {
fallback = true;
goto create_child;
}
new_msk = mptcp_sk_clone(listener->conn, &mp_opt, req);
if (!new_msk)
fallback = true;
} else if (subflow_req->mp_join) {
mptcp_get_options(skb, &mp_opt);
if (!(mp_opt.suboptions & OPTIONS_MPTCP_MPJ) ||
!subflow_hmac_valid(req, &mp_opt) ||
!mptcp_can_accept_new_subflow(subflow_req->msk)) {
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKMAC);
fallback = true;
}
}
create_child:
child = listener->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
req_unhash, own_req);
if (child && *own_req) {
struct mptcp_subflow_context *ctx = mptcp_subflow_ctx(child);
tcp_rsk(req)->drop_req = false;
/* we need to fallback on ctx allocation failure and on pre-reqs
* checking above. In the latter scenario we additionally need
* to reset the context to non MPTCP status.
*/
if (!ctx || fallback) {
if (fallback_is_fatal) {
subflow_add_reset_reason(skb, MPTCP_RST_EMPTCP);
goto dispose_child;
}
subflow_drop_ctx(child);
goto out;
}
/* ssk inherits options of listener sk */
ctx->setsockopt_seq = listener->setsockopt_seq;
if (ctx->mp_capable) {
/* this can't race with mptcp_close(), as the msk is
* not yet exposted to user-space
*/
inet_sk_state_store((void *)new_msk, TCP_ESTABLISHED);
/* record the newly created socket as the first msk
* subflow, but don't link it yet into conn_list
*/
WRITE_ONCE(mptcp_sk(new_msk)->first, child);
/* new mpc subflow takes ownership of the newly
* created mptcp socket
*/
new_msk->sk_destruct = mptcp_sock_destruct;
mptcp_sk(new_msk)->setsockopt_seq = ctx->setsockopt_seq;
mptcp_pm_new_connection(mptcp_sk(new_msk), child, 1);
mptcp_token_accept(subflow_req, mptcp_sk(new_msk));
ctx->conn = new_msk;
new_msk = NULL;
/* with OoO packets we can reach here without ingress
* mpc option
*/
if (mp_opt.suboptions & OPTIONS_MPTCP_MPC)
mptcp_subflow_fully_established(ctx, &mp_opt);
} else if (ctx->mp_join) {
struct mptcp_sock *owner;
owner = subflow_req->msk;
if (!owner) {
subflow_add_reset_reason(skb, MPTCP_RST_EPROHIBIT);
goto dispose_child;
}
/* move the msk reference ownership to the subflow */
subflow_req->msk = NULL;
ctx->conn = (struct sock *)owner;
if (subflow_use_different_sport(owner, sk)) {
pr_debug("ack inet_sport=%d %d",
ntohs(inet_sk(sk)->inet_sport),
ntohs(inet_sk((struct sock *)owner)->inet_sport));
if (!mptcp_pm_sport_in_anno_list(owner, sk)) {
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_MISMATCHPORTACKRX);
goto dispose_child;
}
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINPORTACKRX);
}
if (!mptcp_finish_join(child))
goto dispose_child;
SUBFLOW_REQ_INC_STATS(req, MPTCP_MIB_JOINACKRX);
tcp_rsk(req)->drop_req = true;
}
}
out:
/* dispose of the left over mptcp master, if any */
if (unlikely(new_msk))
mptcp_force_close(new_msk);
/* check for expected invariant - should never trigger, just help
* catching eariler subtle bugs
*/
WARN_ON_ONCE(child && *own_req && tcp_sk(child)->is_mptcp &&
(!mptcp_subflow_ctx(child) ||
!mptcp_subflow_ctx(child)->conn));
return child;
dispose_child:
subflow_drop_ctx(child);
tcp_rsk(req)->drop_req = true;
inet_csk_prepare_for_destroy_sock(child);
tcp_done(child);
req->rsk_ops->send_reset(sk, skb);
/* The last child reference will be released by the caller */
return child;
}
static struct inet_connection_sock_af_ops subflow_specific __ro_after_init;
static struct proto tcp_prot_override;
enum mapping_status {
MAPPING_OK,
MAPPING_INVALID,
MAPPING_EMPTY,
MAPPING_DATA_FIN,
MAPPING_DUMMY
};
static void dbg_bad_map(struct mptcp_subflow_context *subflow, u32 ssn)
{
pr_debug("Bad mapping: ssn=%d map_seq=%d map_data_len=%d",
ssn, subflow->map_subflow_seq, subflow->map_data_len);
}
static bool skb_is_fully_mapped(struct sock *ssk, struct sk_buff *skb)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
unsigned int skb_consumed;
skb_consumed = tcp_sk(ssk)->copied_seq - TCP_SKB_CB(skb)->seq;
if (WARN_ON_ONCE(skb_consumed >= skb->len))
return true;
return skb->len - skb_consumed <= subflow->map_data_len -
mptcp_subflow_get_map_offset(subflow);
}
static bool validate_mapping(struct sock *ssk, struct sk_buff *skb)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
u32 ssn = tcp_sk(ssk)->copied_seq - subflow->ssn_offset;
if (unlikely(before(ssn, subflow->map_subflow_seq))) {
/* Mapping covers data later in the subflow stream,
* currently unsupported.
*/
dbg_bad_map(subflow, ssn);
return false;
}
if (unlikely(!before(ssn, subflow->map_subflow_seq +
subflow->map_data_len))) {
/* Mapping does covers past subflow data, invalid */
dbg_bad_map(subflow, ssn);
return false;
}
return true;
}
static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *skb,
bool csum_reqd)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
u32 offset, seq, delta;
__sum16 csum;
int len;
if (!csum_reqd)
return MAPPING_OK;
/* mapping already validated on previous traversal */
if (subflow->map_csum_len == subflow->map_data_len)
return MAPPING_OK;
/* traverse the receive queue, ensuring it contains a full
* DSS mapping and accumulating the related csum.
* Preserve the accoumlate csum across multiple calls, to compute
* the csum only once
*/
delta = subflow->map_data_len - subflow->map_csum_len;
for (;;) {
seq = tcp_sk(ssk)->copied_seq + subflow->map_csum_len;
offset = seq - TCP_SKB_CB(skb)->seq;
/* if the current skb has not been accounted yet, csum its contents
* up to the amount covered by the current DSS
*/
if (offset < skb->len) {
__wsum csum;
len = min(skb->len - offset, delta);
csum = skb_checksum(skb, offset, len, 0);
subflow->map_data_csum = csum_block_add(subflow->map_data_csum, csum,
subflow->map_csum_len);
delta -= len;
subflow->map_csum_len += len;
}
if (delta == 0)
break;
if (skb_queue_is_last(&ssk->sk_receive_queue, skb)) {
/* if this subflow is closed, the partial mapping
* will be never completed; flush the pending skbs, so
* that subflow_sched_work_if_closed() can kick in
*/
if (unlikely(ssk->sk_state == TCP_CLOSE))
while ((skb = skb_peek(&ssk->sk_receive_queue)))
sk_eat_skb(ssk, skb);
/* not enough data to validate the csum */
return MAPPING_EMPTY;
}
/* the DSS mapping for next skbs will be validated later,
* when a get_mapping_status call will process such skb
*/
skb = skb->next;
}
/* note that 'map_data_len' accounts only for the carried data, does
* not include the eventual seq increment due to the data fin,
* while the pseudo header requires the original DSS data len,
* including that
*/
csum = __mptcp_make_csum(subflow->map_seq,
subflow->map_subflow_seq,
subflow->map_data_len + subflow->map_data_fin,
subflow->map_data_csum);
if (unlikely(csum)) {
MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
if (subflow->mp_join || subflow->valid_csum_seen) {
subflow->send_mp_fail = 1;
MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPFAILTX);
}
return subflow->mp_join ? MAPPING_INVALID : MAPPING_DUMMY;
}
subflow->valid_csum_seen = 1;
return MAPPING_OK;
}
static enum mapping_status get_mapping_status(struct sock *ssk,
struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
bool csum_reqd = READ_ONCE(msk->csum_enabled);
struct sock *sk = (struct sock *)msk;
struct mptcp_ext *mpext;
struct sk_buff *skb;
u16 data_len;
u64 map_seq;
skb = skb_peek(&ssk->sk_receive_queue);
if (!skb)
return MAPPING_EMPTY;
if (mptcp_check_fallback(ssk))
return MAPPING_DUMMY;
mpext = mptcp_get_ext(skb);
if (!mpext || !mpext->use_map) {
if (!subflow->map_valid && !skb->len) {
/* the TCP stack deliver 0 len FIN pkt to the receive
* queue, that is the only 0len pkts ever expected here,
* and we can admit no mapping only for 0 len pkts
*/
if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN))
WARN_ONCE(1, "0len seq %d:%d flags %x",
TCP_SKB_CB(skb)->seq,
TCP_SKB_CB(skb)->end_seq,