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protocol.c
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protocol.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 <linux/sched/signal.h>
#include <linux/atomic.h>
#include <net/sock.h>
#include <net/inet_common.h>
#include <net/inet_hashtables.h>
#include <net/protocol.h>
#include <net/tcp.h>
#include <net/tcp_states.h>
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
#include <net/transp_v6.h>
#endif
#include <net/mptcp.h>
#include "protocol.h"
#include "mib.h"
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
struct mptcp6_sock {
struct mptcp_sock msk;
struct ipv6_pinfo np;
};
#endif
struct mptcp_skb_cb {
u64 map_seq;
u64 end_seq;
u32 offset;
};
#define MPTCP_SKB_CB(__skb) ((struct mptcp_skb_cb *)&((__skb)->cb[0]))
static struct percpu_counter mptcp_sockets_allocated;
/* If msk has an initial subflow socket, and the MP_CAPABLE handshake has not
* completed yet or has failed, return the subflow socket.
* Otherwise return NULL.
*/
static struct socket *__mptcp_nmpc_socket(const struct mptcp_sock *msk)
{
if (!msk->subflow || READ_ONCE(msk->can_ack))
return NULL;
return msk->subflow;
}
static bool mptcp_is_tcpsk(struct sock *sk)
{
struct socket *sock = sk->sk_socket;
if (unlikely(sk->sk_prot == &tcp_prot)) {
/* we are being invoked after mptcp_accept() has
* 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 true;
#if IS_ENABLED(CONFIG_MPTCP_IPV6)
} else if (unlikely(sk->sk_prot == &tcpv6_prot)) {
sock->ops = &inet6_stream_ops;
return true;
#endif
}
return false;
}
static struct sock *__mptcp_tcp_fallback(struct mptcp_sock *msk)
{
sock_owned_by_me((const struct sock *)msk);
if (likely(!__mptcp_check_fallback(msk)))
return NULL;
return msk->first;
}
static int __mptcp_socket_create(struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow;
struct sock *sk = (struct sock *)msk;
struct socket *ssock;
int err;
err = mptcp_subflow_create_socket(sk, &ssock);
if (err)
return err;
msk->first = ssock->sk;
msk->subflow = ssock;
subflow = mptcp_subflow_ctx(ssock->sk);
list_add(&subflow->node, &msk->conn_list);
subflow->request_mptcp = 1;
/* accept() will wait on first subflow sk_wq, and we always wakes up
* via msk->sk_socket
*/
RCU_INIT_POINTER(msk->first->sk_wq, &sk->sk_socket->wq);
return 0;
}
static void mptcp_drop(struct sock *sk, struct sk_buff *skb)
{
sk_drops_add(sk, skb);
__kfree_skb(skb);
}
static bool mptcp_try_coalesce(struct sock *sk, struct sk_buff *to,
struct sk_buff *from)
{
bool fragstolen;
int delta;
if (MPTCP_SKB_CB(from)->offset ||
!skb_try_coalesce(to, from, &fragstolen, &delta))
return false;
pr_debug("colesced seq %llx into %llx new len %d new end seq %llx",
MPTCP_SKB_CB(from)->map_seq, MPTCP_SKB_CB(to)->map_seq,
to->len, MPTCP_SKB_CB(from)->end_seq);
MPTCP_SKB_CB(to)->end_seq = MPTCP_SKB_CB(from)->end_seq;
kfree_skb_partial(from, fragstolen);
atomic_add(delta, &sk->sk_rmem_alloc);
sk_mem_charge(sk, delta);
return true;
}
static bool mptcp_ooo_try_coalesce(struct mptcp_sock *msk, struct sk_buff *to,
struct sk_buff *from)
{
if (MPTCP_SKB_CB(from)->map_seq != MPTCP_SKB_CB(to)->end_seq)
return false;
return mptcp_try_coalesce((struct sock *)msk, to, from);
}
/* "inspired" by tcp_data_queue_ofo(), main differences:
* - use mptcp seqs
* - don't cope with sacks
*/
static void mptcp_data_queue_ofo(struct mptcp_sock *msk, struct sk_buff *skb)
{
struct sock *sk = (struct sock *)msk;
struct rb_node **p, *parent;
u64 seq, end_seq, max_seq;
struct sk_buff *skb1;
int space;
seq = MPTCP_SKB_CB(skb)->map_seq;
end_seq = MPTCP_SKB_CB(skb)->end_seq;
space = tcp_space(sk);
max_seq = space > 0 ? space + msk->ack_seq : msk->ack_seq;
pr_debug("msk=%p seq=%llx limit=%llx empty=%d", msk, seq, max_seq,
RB_EMPTY_ROOT(&msk->out_of_order_queue));
if (after64(seq, max_seq)) {
/* out of window */
mptcp_drop(sk, skb);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_NODSSWINDOW);
return;
}
p = &msk->out_of_order_queue.rb_node;
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUE);
if (RB_EMPTY_ROOT(&msk->out_of_order_queue)) {
rb_link_node(&skb->rbnode, NULL, p);
rb_insert_color(&skb->rbnode, &msk->out_of_order_queue);
msk->ooo_last_skb = skb;
goto end;
}
/* with 2 subflows, adding at end of ooo queue is quite likely
* Use of ooo_last_skb avoids the O(Log(N)) rbtree lookup.
*/
if (mptcp_ooo_try_coalesce(msk, msk->ooo_last_skb, skb)) {
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL);
return;
}
/* Can avoid an rbtree lookup if we are adding skb after ooo_last_skb */
if (!before64(seq, MPTCP_SKB_CB(msk->ooo_last_skb)->end_seq)) {
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOQUEUETAIL);
parent = &msk->ooo_last_skb->rbnode;
p = &parent->rb_right;
goto insert;
}
/* Find place to insert this segment. Handle overlaps on the way. */
parent = NULL;
while (*p) {
parent = *p;
skb1 = rb_to_skb(parent);
if (before64(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
p = &parent->rb_left;
continue;
}
if (before64(seq, MPTCP_SKB_CB(skb1)->end_seq)) {
if (!after64(end_seq, MPTCP_SKB_CB(skb1)->end_seq)) {
/* All the bits are present. Drop. */
mptcp_drop(sk, skb);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
return;
}
if (after64(seq, MPTCP_SKB_CB(skb1)->map_seq)) {
/* partial overlap:
* | skb |
* | skb1 |
* continue traversing
*/
} else {
/* skb's seq == skb1's seq and skb covers skb1.
* Replace skb1 with skb.
*/
rb_replace_node(&skb1->rbnode, &skb->rbnode,
&msk->out_of_order_queue);
mptcp_drop(sk, skb1);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
goto merge_right;
}
} else if (mptcp_ooo_try_coalesce(msk, skb1, skb)) {
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_OFOMERGE);
return;
}
p = &parent->rb_right;
}
insert:
/* Insert segment into RB tree. */
rb_link_node(&skb->rbnode, parent, p);
rb_insert_color(&skb->rbnode, &msk->out_of_order_queue);
merge_right:
/* Remove other segments covered by skb. */
while ((skb1 = skb_rb_next(skb)) != NULL) {
if (before64(end_seq, MPTCP_SKB_CB(skb1)->end_seq))
break;
rb_erase(&skb1->rbnode, &msk->out_of_order_queue);
mptcp_drop(sk, skb1);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
}
/* If there is no skb after us, we are the last_skb ! */
if (!skb1)
msk->ooo_last_skb = skb;
end:
skb_condense(skb);
skb_set_owner_r(skb, sk);
}
static bool __mptcp_move_skb(struct mptcp_sock *msk, struct sock *ssk,
struct sk_buff *skb, unsigned int offset,
size_t copy_len)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
struct sock *sk = (struct sock *)msk;
struct sk_buff *tail;
__skb_unlink(skb, &ssk->sk_receive_queue);
skb_ext_reset(skb);
skb_orphan(skb);
/* try to fetch required memory from subflow */
if (!sk_rmem_schedule(sk, skb, skb->truesize)) {
int amount = sk_mem_pages(skb->truesize) << SK_MEM_QUANTUM_SHIFT;
if (ssk->sk_forward_alloc < amount)
goto drop;
ssk->sk_forward_alloc -= amount;
sk->sk_forward_alloc += amount;
}
/* the skb map_seq accounts for the skb offset:
* mptcp_subflow_get_mapped_dsn() is based on the current tp->copied_seq
* value
*/
MPTCP_SKB_CB(skb)->map_seq = mptcp_subflow_get_mapped_dsn(subflow);
MPTCP_SKB_CB(skb)->end_seq = MPTCP_SKB_CB(skb)->map_seq + copy_len;
MPTCP_SKB_CB(skb)->offset = offset;
if (MPTCP_SKB_CB(skb)->map_seq == msk->ack_seq) {
/* in sequence */
WRITE_ONCE(msk->ack_seq, msk->ack_seq + copy_len);
tail = skb_peek_tail(&sk->sk_receive_queue);
if (tail && mptcp_try_coalesce(sk, tail, skb))
return true;
skb_set_owner_r(skb, sk);
__skb_queue_tail(&sk->sk_receive_queue, skb);
return true;
} else if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq)) {
mptcp_data_queue_ofo(msk, skb);
return false;
}
/* old data, keep it simple and drop the whole pkt, sender
* will retransmit as needed, if needed.
*/
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
drop:
mptcp_drop(sk, skb);
return false;
}
static void mptcp_stop_timer(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
mptcp_sk(sk)->timer_ival = 0;
}
static void mptcp_check_data_fin_ack(struct sock *sk)
{
struct mptcp_sock *msk = mptcp_sk(sk);
if (__mptcp_check_fallback(msk))
return;
/* Look for an acknowledged DATA_FIN */
if (((1 << sk->sk_state) &
(TCPF_FIN_WAIT1 | TCPF_CLOSING | TCPF_LAST_ACK)) &&
msk->write_seq == atomic64_read(&msk->snd_una)) {
mptcp_stop_timer(sk);
WRITE_ONCE(msk->snd_data_fin_enable, 0);
switch (sk->sk_state) {
case TCP_FIN_WAIT1:
inet_sk_state_store(sk, TCP_FIN_WAIT2);
sk->sk_state_change(sk);
break;
case TCP_CLOSING:
case TCP_LAST_ACK:
inet_sk_state_store(sk, TCP_CLOSE);
sk->sk_state_change(sk);
break;
}
if (sk->sk_shutdown == SHUTDOWN_MASK ||
sk->sk_state == TCP_CLOSE)
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
else
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
}
}
static bool mptcp_pending_data_fin(struct sock *sk, u64 *seq)
{
struct mptcp_sock *msk = mptcp_sk(sk);
if (READ_ONCE(msk->rcv_data_fin) &&
((1 << sk->sk_state) &
(TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_FIN_WAIT2))) {
u64 rcv_data_fin_seq = READ_ONCE(msk->rcv_data_fin_seq);
if (msk->ack_seq == rcv_data_fin_seq) {
if (seq)
*seq = rcv_data_fin_seq;
return true;
}
}
return false;
}
static void mptcp_set_timeout(const struct sock *sk, const struct sock *ssk)
{
long tout = ssk && inet_csk(ssk)->icsk_pending ?
inet_csk(ssk)->icsk_timeout - jiffies : 0;
if (tout <= 0)
tout = mptcp_sk(sk)->timer_ival;
mptcp_sk(sk)->timer_ival = tout > 0 ? tout : TCP_RTO_MIN;
}
static void mptcp_check_data_fin(struct sock *sk)
{
struct mptcp_sock *msk = mptcp_sk(sk);
u64 rcv_data_fin_seq;
if (__mptcp_check_fallback(msk) || !msk->first)
return;
/* Need to ack a DATA_FIN received from a peer while this side
* of the connection is in ESTABLISHED, FIN_WAIT1, or FIN_WAIT2.
* msk->rcv_data_fin was set when parsing the incoming options
* at the subflow level and the msk lock was not held, so this
* is the first opportunity to act on the DATA_FIN and change
* the msk state.
*
* If we are caught up to the sequence number of the incoming
* DATA_FIN, send the DATA_ACK now and do state transition. If
* not caught up, do nothing and let the recv code send DATA_ACK
* when catching up.
*/
if (mptcp_pending_data_fin(sk, &rcv_data_fin_seq)) {
struct mptcp_subflow_context *subflow;
WRITE_ONCE(msk->ack_seq, msk->ack_seq + 1);
WRITE_ONCE(msk->rcv_data_fin, 0);
sk->sk_shutdown |= RCV_SHUTDOWN;
smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
set_bit(MPTCP_DATA_READY, &msk->flags);
switch (sk->sk_state) {
case TCP_ESTABLISHED:
inet_sk_state_store(sk, TCP_CLOSE_WAIT);
break;
case TCP_FIN_WAIT1:
inet_sk_state_store(sk, TCP_CLOSING);
break;
case TCP_FIN_WAIT2:
inet_sk_state_store(sk, TCP_CLOSE);
// @@ Close subflows now?
break;
default:
/* Other states not expected */
WARN_ON_ONCE(1);
break;
}
mptcp_set_timeout(sk, NULL);
mptcp_for_each_subflow(msk, subflow) {
struct sock *ssk = mptcp_subflow_tcp_sock(subflow);
lock_sock(ssk);
tcp_send_ack(ssk);
release_sock(ssk);
}
sk->sk_state_change(sk);
if (sk->sk_shutdown == SHUTDOWN_MASK ||
sk->sk_state == TCP_CLOSE)
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP);
else
sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN);
}
}
static bool __mptcp_move_skbs_from_subflow(struct mptcp_sock *msk,
struct sock *ssk,
unsigned int *bytes)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
struct sock *sk = (struct sock *)msk;
unsigned int moved = 0;
bool more_data_avail;
struct tcp_sock *tp;
u32 old_copied_seq;
bool done = false;
pr_debug("msk=%p ssk=%p", msk, ssk);
tp = tcp_sk(ssk);
old_copied_seq = tp->copied_seq;
do {
u32 map_remaining, offset;
u32 seq = tp->copied_seq;
struct sk_buff *skb;
bool fin;
/* try to move as much data as available */
map_remaining = subflow->map_data_len -
mptcp_subflow_get_map_offset(subflow);
skb = skb_peek(&ssk->sk_receive_queue);
if (!skb) {
/* if no data is found, a racing workqueue/recvmsg
* already processed the new data, stop here or we
* can enter an infinite loop
*/
if (!moved)
done = true;
break;
}
if (__mptcp_check_fallback(msk)) {
/* if we are running under the workqueue, TCP could have
* collapsed skbs between dummy map creation and now
* be sure to adjust the size
*/
map_remaining = skb->len;
subflow->map_data_len = skb->len;
}
offset = seq - TCP_SKB_CB(skb)->seq;
fin = TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN;
if (fin) {
done = true;
seq++;
}
if (offset < skb->len) {
size_t len = skb->len - offset;
if (tp->urg_data)
done = true;
if (__mptcp_move_skb(msk, ssk, skb, offset, len))
moved += len;
seq += len;
if (WARN_ON_ONCE(map_remaining < len))
break;
} else {
WARN_ON_ONCE(!fin);
sk_eat_skb(ssk, skb);
done = true;
}
WRITE_ONCE(tp->copied_seq, seq);
more_data_avail = mptcp_subflow_data_available(ssk);
if (atomic_read(&sk->sk_rmem_alloc) > READ_ONCE(sk->sk_rcvbuf)) {
done = true;
break;
}
} while (more_data_avail);
*bytes += moved;
if (tp->copied_seq != old_copied_seq)
tcp_cleanup_rbuf(ssk, 1);
return done;
}
static bool mptcp_ofo_queue(struct mptcp_sock *msk)
{
struct sock *sk = (struct sock *)msk;
struct sk_buff *skb, *tail;
bool moved = false;
struct rb_node *p;
u64 end_seq;
p = rb_first(&msk->out_of_order_queue);
pr_debug("msk=%p empty=%d", msk, RB_EMPTY_ROOT(&msk->out_of_order_queue));
while (p) {
skb = rb_to_skb(p);
if (after64(MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq))
break;
p = rb_next(p);
rb_erase(&skb->rbnode, &msk->out_of_order_queue);
if (unlikely(!after64(MPTCP_SKB_CB(skb)->end_seq,
msk->ack_seq))) {
mptcp_drop(sk, skb);
MPTCP_INC_STATS(sock_net(sk), MPTCP_MIB_DUPDATA);
continue;
}
end_seq = MPTCP_SKB_CB(skb)->end_seq;
tail = skb_peek_tail(&sk->sk_receive_queue);
if (!tail || !mptcp_ooo_try_coalesce(msk, tail, skb)) {
int delta = msk->ack_seq - MPTCP_SKB_CB(skb)->map_seq;
/* skip overlapping data, if any */
pr_debug("uncoalesced seq=%llx ack seq=%llx delta=%d",
MPTCP_SKB_CB(skb)->map_seq, msk->ack_seq,
delta);
MPTCP_SKB_CB(skb)->offset += delta;
__skb_queue_tail(&sk->sk_receive_queue, skb);
}
msk->ack_seq = end_seq;
moved = true;
}
return moved;
}
/* In most cases we will be able to lock the mptcp socket. If its already
* owned, we need to defer to the work queue to avoid ABBA deadlock.
*/
static bool move_skbs_to_msk(struct mptcp_sock *msk, struct sock *ssk)
{
struct sock *sk = (struct sock *)msk;
unsigned int moved = 0;
if (READ_ONCE(sk->sk_lock.owned))
return false;
if (unlikely(!spin_trylock_bh(&sk->sk_lock.slock)))
return false;
/* must re-check after taking the lock */
if (!READ_ONCE(sk->sk_lock.owned)) {
__mptcp_move_skbs_from_subflow(msk, ssk, &moved);
mptcp_ofo_queue(msk);
/* If the moves have caught up with the DATA_FIN sequence number
* it's time to ack the DATA_FIN and change socket state, but
* this is not a good place to change state. Let the workqueue
* do it.
*/
if (mptcp_pending_data_fin(sk, NULL) &&
schedule_work(&msk->work))
sock_hold(sk);
}
spin_unlock_bh(&sk->sk_lock.slock);
return moved > 0;
}
void mptcp_data_ready(struct sock *sk, struct sock *ssk)
{
struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
struct mptcp_sock *msk = mptcp_sk(sk);
bool wake;
/* move_skbs_to_msk below can legitly clear the data_avail flag,
* but we will need later to properly woke the reader, cache its
* value
*/
wake = subflow->data_avail == MPTCP_SUBFLOW_DATA_AVAIL;
if (wake)
set_bit(MPTCP_DATA_READY, &msk->flags);
if (atomic_read(&sk->sk_rmem_alloc) < READ_ONCE(sk->sk_rcvbuf) &&
move_skbs_to_msk(msk, ssk))
goto wake;
/* don't schedule if mptcp sk is (still) over limit */
if (atomic_read(&sk->sk_rmem_alloc) > READ_ONCE(sk->sk_rcvbuf))
goto wake;
/* mptcp socket is owned, release_cb should retry */
if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED,
&sk->sk_tsq_flags)) {
sock_hold(sk);
/* need to try again, its possible release_cb() has already
* been called after the test_and_set_bit() above.
*/
move_skbs_to_msk(msk, ssk);
}
wake:
if (wake)
sk->sk_data_ready(sk);
}
static void __mptcp_flush_join_list(struct mptcp_sock *msk)
{
if (likely(list_empty(&msk->join_list)))
return;
spin_lock_bh(&msk->join_list_lock);
list_splice_tail_init(&msk->join_list, &msk->conn_list);
spin_unlock_bh(&msk->join_list_lock);
}
static bool mptcp_timer_pending(struct sock *sk)
{
return timer_pending(&inet_csk(sk)->icsk_retransmit_timer);
}
static void mptcp_reset_timer(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
unsigned long tout;
/* should never be called with mptcp level timer cleared */
tout = READ_ONCE(mptcp_sk(sk)->timer_ival);
if (WARN_ON_ONCE(!tout))
tout = TCP_RTO_MIN;
sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + tout);
}
void mptcp_data_acked(struct sock *sk)
{
mptcp_reset_timer(sk);
if ((!test_bit(MPTCP_SEND_SPACE, &mptcp_sk(sk)->flags) ||
(inet_sk_state_load(sk) != TCP_ESTABLISHED)) &&
schedule_work(&mptcp_sk(sk)->work))
sock_hold(sk);
}
void mptcp_subflow_eof(struct sock *sk)
{
struct mptcp_sock *msk = mptcp_sk(sk);
if (!test_and_set_bit(MPTCP_WORK_EOF, &msk->flags) &&
schedule_work(&msk->work))
sock_hold(sk);
}
static void mptcp_check_for_eof(struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow;
struct sock *sk = (struct sock *)msk;
int receivers = 0;
mptcp_for_each_subflow(msk, subflow)
receivers += !subflow->rx_eof;
if (!receivers && !(sk->sk_shutdown & RCV_SHUTDOWN)) {
/* hopefully temporary hack: propagate shutdown status
* to msk, when all subflows agree on it
*/
sk->sk_shutdown |= RCV_SHUTDOWN;
smp_mb__before_atomic(); /* SHUTDOWN must be visible first */
set_bit(MPTCP_DATA_READY, &msk->flags);
sk->sk_data_ready(sk);
}
}
static bool mptcp_ext_cache_refill(struct mptcp_sock *msk)
{
const struct sock *sk = (const struct sock *)msk;
if (!msk->cached_ext)
msk->cached_ext = __skb_ext_alloc(sk->sk_allocation);
return !!msk->cached_ext;
}
static struct sock *mptcp_subflow_recv_lookup(const struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow;
struct sock *sk = (struct sock *)msk;
sock_owned_by_me(sk);
mptcp_for_each_subflow(msk, subflow) {
if (subflow->data_avail)
return mptcp_subflow_tcp_sock(subflow);
}
return NULL;
}
static bool mptcp_skb_can_collapse_to(u64 write_seq,
const struct sk_buff *skb,
const struct mptcp_ext *mpext)
{
if (!tcp_skb_can_collapse_to(skb))
return false;
/* can collapse only if MPTCP level sequence is in order */
return mpext && mpext->data_seq + mpext->data_len == write_seq;
}
/* we can append data to the given data frag if:
* - there is space available in the backing page_frag
* - the data frag tail matches the current page_frag free offset
* - the data frag end sequence number matches the current write seq
*/
static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
const struct page_frag *pfrag,
const struct mptcp_data_frag *df)
{
return df && pfrag->page == df->page &&
pfrag->offset == (df->offset + df->data_len) &&
df->data_seq + df->data_len == msk->write_seq;
}
static void dfrag_uncharge(struct sock *sk, int len)
{
sk_mem_uncharge(sk, len);
sk_wmem_queued_add(sk, -len);
}
static void dfrag_clear(struct sock *sk, struct mptcp_data_frag *dfrag)
{
int len = dfrag->data_len + dfrag->overhead;
list_del(&dfrag->list);
dfrag_uncharge(sk, len);
put_page(dfrag->page);
}
static bool mptcp_is_writeable(struct mptcp_sock *msk)
{
struct mptcp_subflow_context *subflow;
if (!sk_stream_is_writeable((struct sock *)msk))
return false;
mptcp_for_each_subflow(msk, subflow) {
if (sk_stream_is_writeable(subflow->tcp_sock))
return true;
}
return false;
}
static void mptcp_clean_una(struct sock *sk)
{
struct mptcp_sock *msk = mptcp_sk(sk);
struct mptcp_data_frag *dtmp, *dfrag;
bool cleaned = false;
u64 snd_una;
/* on fallback we just need to ignore snd_una, as this is really
* plain TCP
*/
if (__mptcp_check_fallback(msk))
atomic64_set(&msk->snd_una, msk->write_seq);
snd_una = atomic64_read(&msk->snd_una);
list_for_each_entry_safe(dfrag, dtmp, &msk->rtx_queue, list) {
if (after64(dfrag->data_seq + dfrag->data_len, snd_una))
break;
dfrag_clear(sk, dfrag);
cleaned = true;
}
dfrag = mptcp_rtx_head(sk);
if (dfrag && after64(snd_una, dfrag->data_seq)) {
u64 delta = snd_una - dfrag->data_seq;
if (WARN_ON_ONCE(delta > dfrag->data_len))
goto out;
dfrag->data_seq += delta;
dfrag->offset += delta;
dfrag->data_len -= delta;
dfrag_uncharge(sk, delta);
cleaned = true;
}
out:
if (cleaned) {
sk_mem_reclaim_partial(sk);
/* Only wake up writers if a subflow is ready */
if (mptcp_is_writeable(msk)) {
set_bit(MPTCP_SEND_SPACE, &mptcp_sk(sk)->flags);
smp_mb__after_atomic();
/* set SEND_SPACE before sk_stream_write_space clears
* NOSPACE
*/
sk_stream_write_space(sk);
}
}
}
/* ensure we get enough memory for the frag hdr, beyond some minimal amount of
* data
*/
static bool mptcp_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
{
if (likely(skb_page_frag_refill(32U + sizeof(struct mptcp_data_frag),
pfrag, sk->sk_allocation)))
return true;
sk->sk_prot->enter_memory_pressure(sk);
sk_stream_moderate_sndbuf(sk);
return false;
}
static struct mptcp_data_frag *
mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
int orig_offset)
{
int offset = ALIGN(orig_offset, sizeof(long));
struct mptcp_data_frag *dfrag;
dfrag = (struct mptcp_data_frag *)(page_to_virt(pfrag->page) + offset);
dfrag->data_len = 0;
dfrag->data_seq = msk->write_seq;
dfrag->overhead = offset - orig_offset + sizeof(struct mptcp_data_frag);
dfrag->offset = offset + sizeof(struct mptcp_data_frag);
dfrag->page = pfrag->page;
return dfrag;
}
static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
struct msghdr *msg, struct mptcp_data_frag *dfrag,
long *timeo, int *pmss_now,
int *ps_goal)
{
int mss_now, avail_size, size_goal, offset, ret, frag_truesize = 0;
bool dfrag_collapsed, can_collapse = false;
struct mptcp_sock *msk = mptcp_sk(sk);
struct mptcp_ext *mpext = NULL;
bool retransmission = !!dfrag;
struct sk_buff *skb, *tail;
struct page_frag *pfrag;
struct page *page;
u64 *write_seq;
size_t psize;
/* use the mptcp page cache so that we can easily move the data
* from one substream to another, but do per subflow memory accounting
* Note: pfrag is used only !retransmission, but the compiler if
* fooled into a warning if we don't init here
*/
pfrag = sk_page_frag(sk);
if (!retransmission) {
write_seq = &msk->write_seq;
page = pfrag->page;
} else {
write_seq = &dfrag->data_seq;
page = dfrag->page;
}
/* compute copy limit */
mss_now = tcp_send_mss(ssk, &size_goal, msg->msg_flags);
*pmss_now = mss_now;
*ps_goal = size_goal;
avail_size = size_goal;
skb = tcp_write_queue_tail(ssk);
if (skb) {
mpext = skb_ext_find(skb, SKB_EXT_MPTCP);
/* Limit the write to the size available in the
* current skb, if any, so that we create at most a new skb.
* Explicitly tells TCP internals to avoid collapsing on later
* queue management operation, to avoid breaking the ext <->
* SSN association set here
*/
can_collapse = (size_goal - skb->len > 0) &&
mptcp_skb_can_collapse_to(*write_seq, skb, mpext);
if (!can_collapse)
TCP_SKB_CB(skb)->eor = 1;
else
avail_size = size_goal - skb->len;
}
if (!retransmission) {
/* reuse tail pfrag, if possible, or carve a new one from the
* page allocator
*/
dfrag = mptcp_rtx_tail(sk);
offset = pfrag->offset;
dfrag_collapsed = mptcp_frag_can_collapse_to(msk, pfrag, dfrag);
if (!dfrag_collapsed) {
dfrag = mptcp_carve_data_frag(msk, pfrag, offset);
offset = dfrag->offset;
frag_truesize = dfrag->overhead;
}
psize = min_t(size_t, pfrag->size - offset, avail_size);
/* Copy to page */
pr_debug("left=%zu", msg_data_left(msg));
psize = copy_page_from_iter(pfrag->page, offset,
min_t(size_t, msg_data_left(msg),
psize),
&msg->msg_iter);
pr_debug("left=%zu", msg_data_left(msg));
if (!psize)
return -EINVAL;
if (!sk_wmem_schedule(sk, psize + dfrag->overhead)) {
iov_iter_revert(&msg->msg_iter, psize);
return -ENOMEM;
}
} else {
offset = dfrag->offset;
psize = min_t(size_t, dfrag->data_len, avail_size);
}
/* tell the TCP stack to delay the push so that we can safely
* access the skb after the sendpages call
*/
ret = do_tcp_sendpages(ssk, page, offset, psize,
msg->msg_flags | MSG_SENDPAGE_NOTLAST | MSG_DONTWAIT);
if (ret <= 0) {
if (!retransmission)
iov_iter_revert(&msg->msg_iter, psize);
return ret;
}
frag_truesize += ret;
if (!retransmission) {
if (unlikely(ret < psize))
iov_iter_revert(&msg->msg_iter, psize - ret);
/* send successful, keep track of sent data for mptcp-level
* retransmission
*/
dfrag->data_len += ret;
if (!dfrag_collapsed) {
get_page(dfrag->page);
list_add_tail(&dfrag->list, &msk->rtx_queue);
sk_wmem_queued_add(sk, frag_truesize);