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Message-Id: <20200323212642.34104-12-mathew.j.martineau@linux.intel.com>
Date: Mon, 23 Mar 2020 14:26:36 -0700
From: Mat Martineau <mathew.j.martineau@...ux.intel.com>
To: netdev@...r.kernel.org
Cc: Paolo Abeni <pabeni@...hat.com>, eric.dumazet@...il.com,
Florian Westphal <fw@...len.de>,
Mat Martineau <mathew.j.martineau@...ux.intel.com>
Subject: [PATCH net-next 11/17] mptcp: rework mptcp_sendmsg_frag to accept optional dfrag
From: Paolo Abeni <pabeni@...hat.com>
This will simplify mptcp-level retransmission implementation
in the next patch. If dfrag is provided by the caller, skip
kernel space memory allocation and use data and metadata
provided by the dfrag itself.
Because a peer could ack data at TCP level but refrain from
sending mptcp-level ACKs, we could grow the mptcp socket
backlog indefinitely.
We should thus block mptcp_sendmsg until the peer has acked some of the
sent data.
In order to be able to do so, increment the mptcp socket wmem_queued
counter on memory allocation and decrement it when releasing the memory
on mptcp-level ack reception.
Because TCP performns sndbuf auto-tuning up to tcp_wmem_max[2], make
this the mptcp sk_sndbuf limit.
In the future we could add experiment with autotuning as TCP does in
tcp_sndbuf_expand().
Co-developed-by: Florian Westphal <fw@...len.de>
Signed-off-by: Florian Westphal <fw@...len.de>
Signed-off-by: Paolo Abeni <pabeni@...hat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
---
net/mptcp/protocol.c | 119 ++++++++++++++++++++++++++-----------------
1 file changed, 72 insertions(+), 47 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index d4b6ce984576..c7a333a6d917 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -316,7 +316,7 @@ static struct sock *mptcp_subflow_recv_lookup(const struct mptcp_sock *msk)
return NULL;
}
-static inline bool mptcp_skb_can_collapse_to(const struct mptcp_sock *msk,
+static inline bool mptcp_skb_can_collapse_to(u64 write_seq,
const struct sk_buff *skb,
const struct mptcp_ext *mpext)
{
@@ -324,7 +324,7 @@ static inline bool mptcp_skb_can_collapse_to(const struct mptcp_sock *msk,
return false;
/* can collapse only if MPTCP level sequence is in order */
- return mpext && mpext->data_seq + mpext->data_len == msk->write_seq;
+ return mpext && mpext->data_seq + mpext->data_len == write_seq;
}
static inline bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
@@ -417,23 +417,28 @@ mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
}
static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
- struct msghdr *msg, long *timeo, int *pmss_now,
+ 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;
- struct mptcp_data_frag *dfrag;
+ 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);
- while (!mptcp_page_frag_refill(ssk, pfrag) ||
+ while ((!retransmission && !mptcp_page_frag_refill(ssk, pfrag)) ||
!mptcp_ext_cache_refill(msk)) {
ret = sk_stream_wait_memory(ssk, timeo);
if (ret)
@@ -447,6 +452,13 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
if (unlikely(__mptcp_needs_tcp_fallback(msk)))
return 0;
}
+ 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);
@@ -464,63 +476,74 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
* SSN association set here
*/
can_collapse = (size_goal - skb->len > 0) &&
- mptcp_skb_can_collapse_to(msk, skb, mpext);
+ 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;
}
- /* 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);
+ 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))
+ return -ENOMEM;
+ } else {
offset = dfrag->offset;
- frag_truesize = dfrag->overhead;
+ psize = min_t(size_t, dfrag->data_len, avail_size);
}
- 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))
- return -ENOMEM;
/* 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, pfrag->page, offset, psize,
+ ret = do_tcp_sendpages(ssk, page, offset, psize,
msg->msg_flags | MSG_SENDPAGE_NOTLAST);
if (ret <= 0)
return ret;
frag_truesize += ret;
- if (unlikely(ret < psize))
- iov_iter_revert(&msg->msg_iter, psize - 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);
- }
+ /* 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);
+ } else {
+ sk_wmem_queued_add(sk, ret);
+ }
- /* charge data on mptcp rtx queue to the master socket
- * Note: we charge such data both to sk and ssk
- */
- sk->sk_forward_alloc -= frag_truesize;
+ /* charge data on mptcp rtx queue to the master socket
+ * Note: we charge such data both to sk and ssk
+ */
+ sk->sk_forward_alloc -= frag_truesize;
+ }
/* if the tail skb extension is still the cached one, collapsing
* really happened. Note: we can't check for 'same skb' as the sk_buff
@@ -539,7 +562,7 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
msk->cached_ext = NULL;
memset(mpext, 0, sizeof(*mpext));
- mpext->data_seq = msk->write_seq;
+ mpext->data_seq = *write_seq;
mpext->subflow_seq = mptcp_subflow_ctx(ssk)->rel_write_seq;
mpext->data_len = ret;
mpext->use_map = 1;
@@ -550,8 +573,9 @@ static int mptcp_sendmsg_frag(struct sock *sk, struct sock *ssk,
mpext->dsn64);
out:
- pfrag->offset += frag_truesize;
- msk->write_seq += ret;
+ if (!retransmission)
+ pfrag->offset += frag_truesize;
+ *write_seq += ret;
mptcp_subflow_ctx(ssk)->rel_write_seq += ret;
return ret;
@@ -663,7 +687,7 @@ static int mptcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
lock_sock(ssk);
while (msg_data_left(msg)) {
- ret = mptcp_sendmsg_frag(sk, ssk, msg, &timeo, &mss_now,
+ ret = mptcp_sendmsg_frag(sk, ssk, msg, NULL, &timeo, &mss_now,
&size_goal);
if (ret < 0)
break;
@@ -974,6 +998,7 @@ static int mptcp_init_sock(struct sock *sk)
return ret;
sk_sockets_allocated_inc(sk);
+ sk->sk_sndbuf = sock_net(sk)->ipv4.sysctl_tcp_wmem[2];
if (!mptcp_is_enabled(sock_net(sk)))
return -ENOPROTOOPT;
--
2.26.0
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