Release 4.11 net/rxrpc/input.c

/* RxRPC packet reception
 *
 * Copyright (C) 2007, 2016 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */


#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/net.h>
#include <linux/skbuff.h>
#include <linux/errqueue.h>
#include <linux/udp.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/icmp.h>
#include <linux/gfp.h>
#include <net/sock.h>
#include <net/af_rxrpc.h>
#include <net/ip.h>
#include <net/udp.h>
#include <net/net_namespace.h>
#include "ar-internal.h"



static void rxrpc_proto_abort(const char *why,
			      struct rxrpc_call *call, rxrpc_seq_t seq)
{
	if (rxrpc_abort_call(why, call, seq, RX_PROTOCOL_ERROR, EBADMSG)) {
		set_bit(RXRPC_CALL_EV_ABORT, &call->events);
		rxrpc_queue_call(call);
	}
}

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/*
 * Do TCP-style congestion management [RFC 5681].
 */


static void rxrpc_congestion_management(struct rxrpc_call *call,
					struct sk_buff *skb,
					struct rxrpc_ack_summary *summary,
					rxrpc_serial_t acked_serial)
{
	enum rxrpc_congest_change change = rxrpc_cong_no_change;
	unsigned int cumulative_acks = call->cong_cumul_acks;
	unsigned int cwnd = call->cong_cwnd;
	bool resend = false;

	summary->flight_size =
		(call->tx_top - call->tx_hard_ack) - summary->nr_acks;

	if (test_and_clear_bit(RXRPC_CALL_RETRANS_TIMEOUT, &call->flags)) {
		summary->retrans_timeo = true;
		call->cong_ssthresh = max_t(unsigned int,
					    summary->flight_size / 2, 2);
		cwnd = 1;
		if (cwnd >= call->cong_ssthresh &&
		    call->cong_mode == RXRPC_CALL_SLOW_START) {
			call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
			call->cong_tstamp = skb->tstamp;
			cumulative_acks = 0;
		}
	}

	cumulative_acks += summary->nr_new_acks;
	cumulative_acks += summary->nr_rot_new_acks;
	if (cumulative_acks > 255)
		cumulative_acks = 255;

	summary->mode = call->cong_mode;
	summary->cwnd = call->cong_cwnd;
	summary->ssthresh = call->cong_ssthresh;
	summary->cumulative_acks = cumulative_acks;
	summary->dup_acks = call->cong_dup_acks;

	switch (call->cong_mode) {
	case RXRPC_CALL_SLOW_START:
		if (summary->nr_nacks > 0)
			goto packet_loss_detected;
		if (summary->cumulative_acks > 0)
			cwnd += 1;
		if (cwnd >= call->cong_ssthresh) {
			call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
			call->cong_tstamp = skb->tstamp;
		}
		goto out;

	case RXRPC_CALL_CONGEST_AVOIDANCE:
		if (summary->nr_nacks > 0)
			goto packet_loss_detected;

		/* We analyse the number of packets that get ACK'd per RTT
                 * period and increase the window if we managed to fill it.
                 */
		if (call->peer->rtt_usage == 0)
			goto out;
		if (ktime_before(skb->tstamp,
				 ktime_add_ns(call->cong_tstamp,
					      call->peer->rtt)))
			goto out_no_clear_ca;
		change = rxrpc_cong_rtt_window_end;
		call->cong_tstamp = skb->tstamp;
		if (cumulative_acks >= cwnd)
			cwnd++;
		goto out;

	case RXRPC_CALL_PACKET_LOSS:
		if (summary->nr_nacks == 0)
			goto resume_normality;

		if (summary->new_low_nack) {
			change = rxrpc_cong_new_low_nack;
			call->cong_dup_acks = 1;
			if (call->cong_extra > 1)
				call->cong_extra = 1;
			goto send_extra_data;
		}

		call->cong_dup_acks++;
		if (call->cong_dup_acks < 3)
			goto send_extra_data;

		change = rxrpc_cong_begin_retransmission;
		call->cong_mode = RXRPC_CALL_FAST_RETRANSMIT;
		call->cong_ssthresh = max_t(unsigned int,
					    summary->flight_size / 2, 2);
		cwnd = call->cong_ssthresh + 3;
		call->cong_extra = 0;
		call->cong_dup_acks = 0;
		resend = true;
		goto out;

	case RXRPC_CALL_FAST_RETRANSMIT:
		if (!summary->new_low_nack) {
			if (summary->nr_new_acks == 0)
				cwnd += 1;
			call->cong_dup_acks++;
			if (call->cong_dup_acks == 2) {
				change = rxrpc_cong_retransmit_again;
				call->cong_dup_acks = 0;
				resend = true;
			}
		} else {
			change = rxrpc_cong_progress;
			cwnd = call->cong_ssthresh;
			if (summary->nr_nacks == 0)
				goto resume_normality;
		}
		goto out;

	default:
		BUG();
		goto out;
	}

resume_normality:
	change = rxrpc_cong_cleared_nacks;
	call->cong_dup_acks = 0;
	call->cong_extra = 0;
	call->cong_tstamp = skb->tstamp;
	if (cwnd < call->cong_ssthresh)
		call->cong_mode = RXRPC_CALL_SLOW_START;
	else
		call->cong_mode = RXRPC_CALL_CONGEST_AVOIDANCE;
out:
	cumulative_acks = 0;
out_no_clear_ca:
	if (cwnd >= RXRPC_RXTX_BUFF_SIZE - 1)
		cwnd = RXRPC_RXTX_BUFF_SIZE - 1;
	call->cong_cwnd = cwnd;
	call->cong_cumul_acks = cumulative_acks;
	trace_rxrpc_congest(call, summary, acked_serial, change);
	if (resend && !test_and_set_bit(RXRPC_CALL_EV_RESEND, &call->events))
		rxrpc_queue_call(call);
	return;

packet_loss_detected:
	change = rxrpc_cong_saw_nack;
	call->cong_mode = RXRPC_CALL_PACKET_LOSS;
	call->cong_dup_acks = 0;
	goto send_extra_data;

send_extra_data:
	/* Send some previously unsent DATA if we have some to advance the ACK
         * state.
         */
	if (call->rxtx_annotations[call->tx_top & RXRPC_RXTX_BUFF_MASK] &
	    RXRPC_TX_ANNO_LAST ||
	    summary->nr_acks != call->tx_top - call->tx_hard_ack) {
		call->cong_extra++;
		wake_up(&call->waitq);
	}
	goto out_no_clear_ca;
}

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/*
 * Ping the other end to fill our RTT cache and to retrieve the rwind
 * and MTU parameters.
 */


static void rxrpc_send_ping(struct rxrpc_call *call, struct sk_buff *skb,
			    int skew)
{
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	ktime_t now = skb->tstamp;

	if (call->peer->rtt_usage < 3 ||
	    ktime_before(ktime_add_ms(call->peer->rtt_last_req, 1000), now))
		rxrpc_propose_ACK(call, RXRPC_ACK_PING, skew, sp->hdr.serial,
				  true, true,
				  rxrpc_propose_ack_ping_for_params);
}

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/*
 * Apply a hard ACK by advancing the Tx window.
 */


static void rxrpc_rotate_tx_window(struct rxrpc_call *call, rxrpc_seq_t to,
				   struct rxrpc_ack_summary *summary)
{
	struct sk_buff *skb, *list = NULL;
	int ix;
	u8 annotation;

	if (call->acks_lowest_nak == call->tx_hard_ack) {
		call->acks_lowest_nak = to;
	} else if (before_eq(call->acks_lowest_nak, to)) {
		summary->new_low_nack = true;
		call->acks_lowest_nak = to;
	}

	spin_lock(&call->lock);

	while (before(call->tx_hard_ack, to)) {
		call->tx_hard_ack++;
		ix = call->tx_hard_ack & RXRPC_RXTX_BUFF_MASK;
		skb = call->rxtx_buffer[ix];
		annotation = call->rxtx_annotations[ix];
		rxrpc_see_skb(skb, rxrpc_skb_tx_rotated);
		call->rxtx_buffer[ix] = NULL;
		call->rxtx_annotations[ix] = 0;
		skb->next = list;
		list = skb;

		if (annotation & RXRPC_TX_ANNO_LAST)
			set_bit(RXRPC_CALL_TX_LAST, &call->flags);
		if ((annotation & RXRPC_TX_ANNO_MASK) != RXRPC_TX_ANNO_ACK)
			summary->nr_rot_new_acks++;
	}

	spin_unlock(&call->lock);

	trace_rxrpc_transmit(call, (test_bit(RXRPC_CALL_TX_LAST, &call->flags) ?
				    rxrpc_transmit_rotate_last :
				    rxrpc_transmit_rotate));
	wake_up(&call->waitq);

	while (list) {
		skb = list;
		list = skb->next;
		skb->next = NULL;
		rxrpc_free_skb(skb, rxrpc_skb_tx_freed);
	}
}

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/*
 * End the transmission phase of a call.
 *
 * This occurs when we get an ACKALL packet, the first DATA packet of a reply,
 * or a final ACK packet.
 */


static bool rxrpc_end_tx_phase(struct rxrpc_call *call, bool reply_begun,
			       const char *abort_why)
{

	ASSERT(test_bit(RXRPC_CALL_TX_LAST, &call->flags));

	write_lock(&call->state_lock);

	switch (call->state) {
	case RXRPC_CALL_CLIENT_SEND_REQUEST:
	case RXRPC_CALL_CLIENT_AWAIT_REPLY:
		if (reply_begun)
			call->state = RXRPC_CALL_CLIENT_RECV_REPLY;
		else
			call->state = RXRPC_CALL_CLIENT_AWAIT_REPLY;
		break;

	case RXRPC_CALL_SERVER_AWAIT_ACK:
		__rxrpc_call_completed(call);
		rxrpc_notify_socket(call);
		break;

	default:
		goto bad_state;
	}

	write_unlock(&call->state_lock);
	if (call->state == RXRPC_CALL_CLIENT_AWAIT_REPLY) {
		rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, 0, 0, false, true,
				  rxrpc_propose_ack_client_tx_end);
		trace_rxrpc_transmit(call, rxrpc_transmit_await_reply);
	} else {
		trace_rxrpc_transmit(call, rxrpc_transmit_end);
	}
	_leave(" = ok");
	return true;

bad_state:
	write_unlock(&call->state_lock);
	kdebug("end_tx %s", rxrpc_call_states[call->state]);
	rxrpc_proto_abort(abort_why, call, call->tx_top);
	return false;
}

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/*
 * Begin the reply reception phase of a call.
 */


static bool rxrpc_receiving_reply(struct rxrpc_call *call)
{
	struct rxrpc_ack_summary summary = { 0 };
	rxrpc_seq_t top = READ_ONCE(call->tx_top);

	if (call->ackr_reason) {
		spin_lock_bh(&call->lock);
		call->ackr_reason = 0;
		call->resend_at = call->expire_at;
		call->ack_at = call->expire_at;
		spin_unlock_bh(&call->lock);
		rxrpc_set_timer(call, rxrpc_timer_init_for_reply,
				ktime_get_real());
	}

	if (!test_bit(RXRPC_CALL_TX_LAST, &call->flags))
		rxrpc_rotate_tx_window(call, top, &summary);
	if (!test_bit(RXRPC_CALL_TX_LAST, &call->flags)) {
		rxrpc_proto_abort("TXL", call, top);
		return false;
	}
	if (!rxrpc_end_tx_phase(call, true, "ETD"))
		return false;
	call->tx_phase = false;
	return true;
}

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/*
 * Scan a jumbo packet to validate its structure and to work out how many
 * subpackets it contains.
 *
 * A jumbo packet is a collection of consecutive packets glued together with
 * little headers between that indicate how to change the initial header for
 * each subpacket.
 *
 * RXRPC_JUMBO_PACKET must be set on all but the last subpacket - and all but
 * the last are RXRPC_JUMBO_DATALEN in size.  The last subpacket may be of any
 * size.
 */


static bool rxrpc_validate_jumbo(struct sk_buff *skb)
{
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	unsigned int offset = sizeof(struct rxrpc_wire_header);
	unsigned int len = skb->len;
	int nr_jumbo = 1;
	u8 flags = sp->hdr.flags;

	do {
		nr_jumbo++;
		if (len - offset < RXRPC_JUMBO_SUBPKTLEN)
			goto protocol_error;
		if (flags & RXRPC_LAST_PACKET)
			goto protocol_error;
		offset += RXRPC_JUMBO_DATALEN;
		if (skb_copy_bits(skb, offset, &flags, 1) < 0)
			goto protocol_error;
		offset += sizeof(struct rxrpc_jumbo_header);
	} while (flags & RXRPC_JUMBO_PACKET);

	sp->nr_jumbo = nr_jumbo;
	return true;

protocol_error:
	return false;
}

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/*
 * Handle reception of a duplicate packet.
 *
 * We have to take care to avoid an attack here whereby we're given a series of
 * jumbograms, each with a sequence number one before the preceding one and
 * filled up to maximum UDP size.  If they never send us the first packet in
 * the sequence, they can cause us to have to hold on to around 2MiB of kernel
 * space until the call times out.
 *
 * We limit the space usage by only accepting three duplicate jumbo packets per
 * call.  After that, we tell the other side we're no longer accepting jumbos
 * (that information is encoded in the ACK packet).
 */


static void rxrpc_input_dup_data(struct rxrpc_call *call, rxrpc_seq_t seq,
				 u8 annotation, bool *_jumbo_bad)
{
	/* Discard normal packets that are duplicates. */
	if (annotation == 0)
		return;

	/* Skip jumbo subpackets that are duplicates.  When we've had three or
         * more partially duplicate jumbo packets, we refuse to take any more
         * jumbos for this call.
         */
	if (!*_jumbo_bad) {
		call->nr_jumbo_bad++;
		*_jumbo_bad = true;
	}
}

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/*
 * Process a DATA packet, adding the packet to the Rx ring.
 */


static void rxrpc_input_data(struct rxrpc_call *call, struct sk_buff *skb,
			     u16 skew)
{
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	enum rxrpc_call_state state;
	unsigned int offset = sizeof(struct rxrpc_wire_header);
	unsigned int ix;
	rxrpc_serial_t serial = sp->hdr.serial, ack_serial = 0;
	rxrpc_seq_t seq = sp->hdr.seq, hard_ack;
	bool immediate_ack = false, jumbo_bad = false, queued;
	u16 len;
	u8 ack = 0, flags, annotation = 0;

	_enter("{%u,%u},{%u,%u}",
	       call->rx_hard_ack, call->rx_top, skb->len, seq);

	_proto("Rx DATA %%%u { #%u f=%02x }",
	       sp->hdr.serial, seq, sp->hdr.flags);

	state = READ_ONCE(call->state);
	if (state >= RXRPC_CALL_COMPLETE)
		return;

	/* Received data implicitly ACKs all of the request packets we sent
         * when we're acting as a client.
         */
	if ((state == RXRPC_CALL_CLIENT_SEND_REQUEST ||
	     state == RXRPC_CALL_CLIENT_AWAIT_REPLY) &&
	    !rxrpc_receiving_reply(call))
		return;

	call->ackr_prev_seq = seq;

	hard_ack = READ_ONCE(call->rx_hard_ack);
	if (after(seq, hard_ack + call->rx_winsize)) {
		ack = RXRPC_ACK_EXCEEDS_WINDOW;
		ack_serial = serial;
		goto ack;
	}

	flags = sp->hdr.flags;
	if (flags & RXRPC_JUMBO_PACKET) {
		if (call->nr_jumbo_bad > 3) {
			ack = RXRPC_ACK_NOSPACE;
			ack_serial = serial;
			goto ack;
		}
		annotation = 1;
	}

next_subpacket:
	queued = false;
	ix = seq & RXRPC_RXTX_BUFF_MASK;
	len = skb->len;
	if (flags & RXRPC_JUMBO_PACKET)
		len = RXRPC_JUMBO_DATALEN;

	if (flags & RXRPC_LAST_PACKET) {
		if (test_bit(RXRPC_CALL_RX_LAST, &call->flags) &&
		    seq != call->rx_top)
			return rxrpc_proto_abort("LSN", call, seq);
	} else {
		if (test_bit(RXRPC_CALL_RX_LAST, &call->flags) &&
		    after_eq(seq, call->rx_top))
			return rxrpc_proto_abort("LSA", call, seq);
	}

	trace_rxrpc_rx_data(call, seq, serial, flags, annotation);
	if (before_eq(seq, hard_ack)) {
		ack = RXRPC_ACK_DUPLICATE;
		ack_serial = serial;
		goto skip;
	}

	if (flags & RXRPC_REQUEST_ACK && !ack) {
		ack = RXRPC_ACK_REQUESTED;
		ack_serial = serial;
	}

	if (call->rxtx_buffer[ix]) {
		rxrpc_input_dup_data(call, seq, annotation, &jumbo_bad);
		if (ack != RXRPC_ACK_DUPLICATE) {
			ack = RXRPC_ACK_DUPLICATE;
			ack_serial = serial;
		}
		immediate_ack = true;
		goto skip;
	}

	/* Queue the packet.  We use a couple of memory barriers here as need
         * to make sure that rx_top is perceived to be set after the buffer
         * pointer and that the buffer pointer is set after the annotation and
         * the skb data.
         *
         * Barriers against rxrpc_recvmsg_data() and rxrpc_rotate_rx_window()
         * and also rxrpc_fill_out_ack().
         */
	rxrpc_get_skb(skb, rxrpc_skb_rx_got);
	call->rxtx_annotations[ix] = annotation;
	smp_wmb();
	call->rxtx_buffer[ix] = skb;
	if (after(seq, call->rx_top)) {
		smp_store_release(&call->rx_top, seq);
	} else if (before(seq, call->rx_top)) {
		/* Send an immediate ACK if we fill in a hole */
		if (!ack) {
			ack = RXRPC_ACK_DELAY;
			ack_serial = serial;
		}
		immediate_ack = true;
	}
	if (flags & RXRPC_LAST_PACKET) {
		set_bit(RXRPC_CALL_RX_LAST, &call->flags);
		trace_rxrpc_receive(call, rxrpc_receive_queue_last, serial, seq);
	} else {
		trace_rxrpc_receive(call, rxrpc_receive_queue, serial, seq);
	}
	queued = true;

	if (after_eq(seq, call->rx_expect_next)) {
		if (after(seq, call->rx_expect_next)) {
			_net("OOS %u > %u", seq, call->rx_expect_next);
			ack = RXRPC_ACK_OUT_OF_SEQUENCE;
			ack_serial = serial;
		}
		call->rx_expect_next = seq + 1;
	}

skip:
	offset += len;
	if (flags & RXRPC_JUMBO_PACKET) {
		if (skb_copy_bits(skb, offset, &flags, 1) < 0)
			return rxrpc_proto_abort("XJF", call, seq);
		offset += sizeof(struct rxrpc_jumbo_header);
		seq++;
		serial++;
		annotation++;
		if (flags & RXRPC_JUMBO_PACKET)
			annotation |= RXRPC_RX_ANNO_JLAST;
		if (after(seq, hard_ack + call->rx_winsize)) {
			ack = RXRPC_ACK_EXCEEDS_WINDOW;
			ack_serial = serial;
			if (!jumbo_bad) {
				call->nr_jumbo_bad++;
				jumbo_bad = true;
			}
			goto ack;
		}

		_proto("Rx DATA Jumbo %%%u", serial);
		goto next_subpacket;
	}

	if (queued && flags & RXRPC_LAST_PACKET && !ack) {
		ack = RXRPC_ACK_DELAY;
		ack_serial = serial;
	}

ack:
	if (ack)
		rxrpc_propose_ACK(call, ack, skew, ack_serial,
				  immediate_ack, true,
				  rxrpc_propose_ack_input_data);

	if (sp->hdr.seq == READ_ONCE(call->rx_hard_ack) + 1)
		rxrpc_notify_socket(call);
	_leave(" [queued]");
}

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/*
 * Process a requested ACK.
 */


static void rxrpc_input_requested_ack(struct rxrpc_call *call,
				      ktime_t resp_time,
				      rxrpc_serial_t orig_serial,
				      rxrpc_serial_t ack_serial)
{
	struct rxrpc_skb_priv *sp;
	struct sk_buff *skb;
	ktime_t sent_at;
	int ix;

	for (ix = 0; ix < RXRPC_RXTX_BUFF_SIZE; ix++) {
		skb = call->rxtx_buffer[ix];
		if (!skb)
			continue;

		sp = rxrpc_skb(skb);
		if (sp->hdr.serial != orig_serial)
			continue;
		smp_rmb();
		sent_at = skb->tstamp;
		goto found;
	}
	return;

found:
	rxrpc_peer_add_rtt(call, rxrpc_rtt_rx_requested_ack,
			   orig_serial, ack_serial, sent_at, resp_time);
}

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/*
 * Process a ping response.
 */


static void rxrpc_input_ping_response(struct rxrpc_call *call,
				      ktime_t resp_time,
				      rxrpc_serial_t orig_serial,
				      rxrpc_serial_t ack_serial)
{
	rxrpc_serial_t ping_serial;
	ktime_t ping_time;

	ping_time = call->ping_time;
	smp_rmb();
	ping_serial = call->ping_serial;

	if (!test_bit(RXRPC_CALL_PINGING, &call->flags) ||
	    before(orig_serial, ping_serial))
		return;
	clear_bit(RXRPC_CALL_PINGING, &call->flags);
	if (after(orig_serial, ping_serial))
		return;

	rxrpc_peer_add_rtt(call, rxrpc_rtt_rx_ping_response,
			   orig_serial, ack_serial, ping_time, resp_time);
}

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/*
 * Process the extra information that may be appended to an ACK packet
 */


static void rxrpc_input_ackinfo(struct rxrpc_call *call, struct sk_buff *skb,
				struct rxrpc_ackinfo *ackinfo)
{
	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
	struct rxrpc_peer *peer;
	unsigned int mtu;
	bool wake = false;
	u32 rwind = ntohl(ackinfo->rwind);

	_proto("Rx ACK %%%u Info { rx=%u max=%u rwin=%u jm=%u }",
	       sp->hdr.serial,
	       ntohl(ackinfo->rxMTU), ntohl(ackinfo->maxMTU),
	       rwind, ntohl(ackinfo->jumbo_max));

	if (call->tx_winsize != rwind) {
		if (rwind > RXRPC_RXTX_BUFF_SIZE - 1)
			rwind = RXRPC_RXTX_BUFF_SIZE - 1;
		if (rwind > call->tx_winsize)
			wake = true;
		call->tx_winsize = rwind;
	}

	if (call->cong_ssthresh > rwind)
		call->cong_ssthresh = rwind;

	mtu = min(ntohl(ackinfo->rxMTU), ntohl(ackinfo->maxMTU));

	peer = call->peer;
	if (mtu < peer->maxdata) {
		spin_lock_bh(&peer->lock);
		peer->maxdata = mtu;
		peer->mtu = mtu + peer->hdrsize;
		spin_unlock_bh(&peer->lock);
		_net("Net MTU %u (maxdata %u)", peer->mtu, peer->maxdata);
	}

	if (wake)
		wake_up(&call->waitq);
}

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/*
 * Process individual soft ACKs.
 *
 * Each ACK in the array corresponds to one packet and can be either an ACK or
 * a NAK.  If we get find an explicitly NAK'd packet we resend immediately;
 * packets that lie beyond the end of the ACK list are scheduled for resend by
 * the timer on the basis that the peer might just not have processed them at
 * the time the ACK was sent.
 */


static void rxrpc_input_soft_acks(struct rxrpc_call *call, u8 *acks,
				  rxrpc_seq_t seq, int nr_acks,
				  struct rxrpc_ack_summary *summary)
{
	int ix;
	u8 annotation, anno_type;

	for (; nr_acks > 0; nr_acks--, seq++) {
		ix = seq & RXRPC_RXTX_BUFF_MASK;
		annotation