Commit 355a901e authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

tcp: make connect() mem charging friendly 



While working on sk_forward_alloc problems reported by Denys
Fedoryshchenko, we found that tcp connect() (and fastopen) do not call
sk_wmem_schedule() for SYN packet (and/or SYN/DATA packet), so
sk_forward_alloc is negative while connect is in progress.

We can fix this by calling regular sk_stream_alloc_skb() both for the
SYN packet (in tcp_connect()) and the syn_data packet in
tcp_send_syn_data()

Then, tcp_send_syn_data() can avoid copying syn_data as we simply
can manipulate syn_data->cb[] to remove SYN flag (and increment seq)

Instead of open coding memcpy_fromiovecend(), simply use this helper.

This leaves in socket write queue clean fast clone skbs.

This was tested against our fastopen packetdrill tests.

Reported-by: default avatarDenys Fedoryshchenko <nuclearcat@nuclearcat.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarYuchung Cheng <ycheng@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent baeababb

net/ipv4/tcp_output.c

+28 −40
Original line number Diff line number Diff line
@@ -3011,9 +3011,9 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn) 
{

	struct tcp_sock *tp = tcp_sk(sk);

	struct tcp_fastopen_request *fo = tp->fastopen_req;

	int syn_loss = 0, space, i, err = 0, iovlen = fo->data->msg_iovlen;

	struct sk_buff *syn_data = NULL, *data;

	int syn_loss = 0, space, err = 0;

	unsigned long last_syn_loss = 0;

	struct sk_buff *syn_data;



	tp->rx_opt.mss_clamp = tp->advmss;  /* If MSS is not cached */

	tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie,
@@ -3044,48 +3044,40 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn) 
	/* limit to order-0 allocations */

	space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER));



	syn_data = skb_copy_expand(syn, MAX_TCP_HEADER, space,

				   sk->sk_allocation);

	if (syn_data == NULL)

	syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation);

	if (!syn_data)

		goto fallback;

	syn_data->ip_summed = CHECKSUM_PARTIAL;

	memcpy(syn_data->cb, syn->cb, sizeof(syn->cb));

	if (unlikely(memcpy_fromiovecend(skb_put(syn_data, space),

					 fo->data->msg_iov, 0, space))) {

		kfree_skb(syn_data);

		goto fallback;

	}



	for (i = 0; i < iovlen && syn_data->len < space; ++i) {

		struct iovec *iov = &fo->data->msg_iov[i];

		unsigned char __user *from = iov->iov_base;

		int len = iov->iov_len;



		if (syn_data->len + len > space)

			len = space - syn_data->len;

		else if (i + 1 == iovlen)

	/* No more data pending in inet_wait_for_connect() */

	if (space == fo->size)

		fo->data = NULL;

	fo->copied = space;



		if (skb_add_data(syn_data, from, len))

			goto fallback;

	}

	tcp_connect_queue_skb(sk, syn_data);



	/* Queue a data-only packet after the regular SYN for retransmission */

	data = pskb_copy(syn_data, sk->sk_allocation);

	if (data == NULL)

		goto fallback;

	TCP_SKB_CB(data)->seq++;

	TCP_SKB_CB(data)->tcp_flags &= ~TCPHDR_SYN;

	TCP_SKB_CB(data)->tcp_flags = (TCPHDR_ACK|TCPHDR_PSH);

	tcp_connect_queue_skb(sk, data);

	fo->copied = data->len;

	err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation);



	/* syn_data is about to be sent, we need to take current time stamps

	 * for the packets that are in write queue : SYN packet and DATA

	 */

	skb_mstamp_get(&syn->skb_mstamp);

	data->skb_mstamp = syn->skb_mstamp;

	syn->skb_mstamp = syn_data->skb_mstamp;



	if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) {

	/* Now full SYN+DATA was cloned and sent (or not),

	 * remove the SYN from the original skb (syn_data)

	 * we keep in write queue in case of a retransmit, as we

	 * also have the SYN packet (with no data) in the same queue.

	 */

	TCP_SKB_CB(syn_data)->seq++;

	TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH;

	if (!err) {

		tp->syn_data = (fo->copied > 0);

		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);

		goto done;

	}

	syn_data = NULL;



fallback:

	/* Send a regular SYN with Fast Open cookie request option */
@@ -3094,7 +3086,6 @@ fallback: 
	err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation);

	if (err)

		tp->syn_fastopen = 0;

	kfree_skb(syn_data);

done:

	fo->cookie.len = -1;  /* Exclude Fast Open option for SYN retries */

	return err;
@@ -3114,13 +3105,10 @@ int tcp_connect(struct sock *sk) 
		return 0;

	}



	buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);

	if (unlikely(buff == NULL))

	buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation);

	if (unlikely(!buff))

		return -ENOBUFS;



	/* Reserve space for headers. */

	skb_reserve(buff, MAX_TCP_HEADER);



	tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);

	tp->retrans_stamp = tcp_time_stamp;

	tcp_connect_queue_skb(sk, buff);

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