1/* ar-skbuff.c: socket buffer destruction handling
  2 *
  3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
  4 * Written by David Howells (dhowells@redhat.com)
  5 *
  6 * This program is free software; you can redistribute it and/or
  7 * modify it under the terms of the GNU General Public License
  8 * as published by the Free Software Foundation; either version
  9 * 2 of the License, or (at your option) any later version.
 10 */
 11
 12#include <linux/module.h>
 13#include <linux/net.h>
 14#include <linux/skbuff.h>
 15#include <net/sock.h>
 16#include <net/af_rxrpc.h>
 17#include "ar-internal.h"
 18
 19/*
 20 * set up for the ACK at the end of the receive phase when we discard the final
 21 * receive phase data packet
 22 * - called with softirqs disabled
 23 */
 24static void rxrpc_request_final_ACK(struct rxrpc_call *call)
 25{
 26	/* the call may be aborted before we have a chance to ACK it */
 27	write_lock(&call->state_lock);
 28
 29	switch (call->state) {
 30	case RXRPC_CALL_CLIENT_RECV_REPLY:
 31		call->state = RXRPC_CALL_CLIENT_FINAL_ACK;
 32		_debug("request final ACK");
 33
 34		/* get an extra ref on the call for the final-ACK generator to
 35		 * release */
 36		rxrpc_get_call(call);
 37		set_bit(RXRPC_CALL_EV_ACK_FINAL, &call->events);
 38		if (try_to_del_timer_sync(&call->ack_timer) >= 0)
 39			rxrpc_queue_call(call);
 40		break;
 41
 42	case RXRPC_CALL_SERVER_RECV_REQUEST:
 43		call->state = RXRPC_CALL_SERVER_ACK_REQUEST;
 44	default:
 45		break;
 46	}
 47
 48	write_unlock(&call->state_lock);
 49}
 50
 51/*
 52 * drop the bottom ACK off of the call ACK window and advance the window
 53 */
 54static void rxrpc_hard_ACK_data(struct rxrpc_call *call,
 55				struct rxrpc_skb_priv *sp)
 56{
 57	int loop;
 58	u32 seq;
 59
 60	spin_lock_bh(&call->lock);
 61
 62	_debug("hard ACK #%u", sp->hdr.seq);
 63
 64	for (loop = 0; loop < RXRPC_ACKR_WINDOW_ASZ; loop++) {
 65		call->ackr_window[loop] >>= 1;
 66		call->ackr_window[loop] |=
 67			call->ackr_window[loop + 1] << (BITS_PER_LONG - 1);
 68	}
 69
 70	seq = sp->hdr.seq;
 71	ASSERTCMP(seq, ==, call->rx_data_eaten + 1);
 72	call->rx_data_eaten = seq;
 73
 74	if (call->ackr_win_top < UINT_MAX)
 75		call->ackr_win_top++;
 76
 77	ASSERTIFCMP(call->state <= RXRPC_CALL_COMPLETE,
 78		    call->rx_data_post, >=, call->rx_data_recv);
 79	ASSERTIFCMP(call->state <= RXRPC_CALL_COMPLETE,
 80		    call->rx_data_recv, >=, call->rx_data_eaten);
 81
 82	if (sp->hdr.flags & RXRPC_LAST_PACKET) {
 83		rxrpc_request_final_ACK(call);
 84	} else if (atomic_dec_and_test(&call->ackr_not_idle) &&
 85		   test_and_clear_bit(RXRPC_CALL_TX_SOFT_ACK, &call->flags)) {
 86		/* We previously soft-ACK'd some received packets that have now
 87		 * been consumed, so send a hard-ACK if no more packets are
 88		 * immediately forthcoming to allow the transmitter to free up
 89		 * its Tx bufferage.
 90		 */
 91		_debug("send Rx idle ACK");
 92		__rxrpc_propose_ACK(call, RXRPC_ACK_IDLE, sp->hdr.serial,
 93				    false);
 94	}
 95
 96	spin_unlock_bh(&call->lock);
 97}
 98
 99/*
100 * destroy a packet that has an RxRPC control buffer
101 * - advance the hard-ACK state of the parent call (done here in case something
102 *   in the kernel bypasses recvmsg() and steals the packet directly off of the
103 *   socket receive queue)
104 */
105void rxrpc_packet_destructor(struct sk_buff *skb)
106{
107	struct rxrpc_skb_priv *sp = rxrpc_skb(skb);
108	struct rxrpc_call *call = sp->call;
109
110	_enter("%p{%p}", skb, call);
111
112	if (call) {
113		/* send the final ACK on a client call */
114		if (sp->hdr.type == RXRPC_PACKET_TYPE_DATA)
115			rxrpc_hard_ACK_data(call, sp);
116		rxrpc_put_call(call);
117		sp->call = NULL;
118	}
119
120	if (skb->sk)
121		sock_rfree(skb);
122	_leave("");
123}
124
125/**
126 * rxrpc_kernel_free_skb - Free an RxRPC socket buffer
127 * @skb: The socket buffer to be freed
128 *
129 * Let RxRPC free its own socket buffer, permitting it to maintain debug
130 * accounting.
131 */
132void rxrpc_kernel_free_skb(struct sk_buff *skb)
133{
134	rxrpc_free_skb(skb);
135}
136EXPORT_SYMBOL(rxrpc_kernel_free_skb);