input.c

linux 内核源代码

/*
 *  net/dccp/input.c
 *
 *  An implementation of the DCCP protocol
 *  Arnaldo Carvalho de Melo <[e-mail]>
 *
 *	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.
 */

#include <linux/dccp.h>
#include <linux/skbuff.h>

#include <net/sock.h>

#include "ackvec.h"
#include "ccid.h"
#include "dccp.h"

/* rate-limit for syncs in reply to sequence-invalid packets; RFC 4340, 7.5.4 */
int sysctl_dccp_sync_ratelimit	__read_mostly = HZ / 8;

static void dccp_fin(struct sock *sk, struct sk_buff *skb)
{
	sk->sk_shutdown |= RCV_SHUTDOWN;
	sock_set_flag(sk, SOCK_DONE);
	__skb_pull(skb, dccp_hdr(skb)->dccph_doff * 4);
	__skb_queue_tail(&sk->sk_receive_queue, skb);
	skb_set_owner_r(skb, sk);
	sk->sk_data_ready(sk, 0);
}

static void dccp_rcv_close(struct sock *sk, struct sk_buff *skb)
{
	dccp_send_reset(sk, DCCP_RESET_CODE_CLOSED);
	dccp_fin(sk, skb);
	dccp_set_state(sk, DCCP_CLOSED);
	sk_wake_async(sk, 1, POLL_HUP);
}

static void dccp_rcv_closereq(struct sock *sk, struct sk_buff *skb)
{
	/*
	 *   Step 7: Check for unexpected packet types
	 *      If (S.is_server and P.type == CloseReq)
	 *	  Send Sync packet acknowledging P.seqno
	 *	  Drop packet and return
	 */
	if (dccp_sk(sk)->dccps_role != DCCP_ROLE_CLIENT) {
		dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq, DCCP_PKT_SYNC);
		return;
	}

	if (sk->sk_state != DCCP_CLOSING)
		dccp_set_state(sk, DCCP_CLOSING);
	dccp_send_close(sk, 0);
}

static u8 dccp_reset_code_convert(const u8 code)
{
	const u8 error_code[] = {
	[DCCP_RESET_CODE_CLOSED]	     = 0,	/* normal termination */
	[DCCP_RESET_CODE_UNSPECIFIED]	     = 0,	/* nothing known */
	[DCCP_RESET_CODE_ABORTED]	     = ECONNRESET,

	[DCCP_RESET_CODE_NO_CONNECTION]	     = ECONNREFUSED,
	[DCCP_RESET_CODE_CONNECTION_REFUSED] = ECONNREFUSED,
	[DCCP_RESET_CODE_TOO_BUSY]	     = EUSERS,
	[DCCP_RESET_CODE_AGGRESSION_PENALTY] = EDQUOT,

	[DCCP_RESET_CODE_PACKET_ERROR]	     = ENOMSG,
	[DCCP_RESET_CODE_BAD_INIT_COOKIE]    = EBADR,
	[DCCP_RESET_CODE_BAD_SERVICE_CODE]   = EBADRQC,
	[DCCP_RESET_CODE_OPTION_ERROR]	     = EILSEQ,
	[DCCP_RESET_CODE_MANDATORY_ERROR]    = EOPNOTSUPP,
	};

	return code >= DCCP_MAX_RESET_CODES ? 0 : error_code[code];
}

static void dccp_rcv_reset(struct sock *sk, struct sk_buff *skb)
{
	u8 err = dccp_reset_code_convert(dccp_hdr_reset(skb)->dccph_reset_code);

	sk->sk_err = err;

	/* Queue the equivalent of TCP fin so that dccp_recvmsg exits the loop */
	dccp_fin(sk, skb);

	if (err && !sock_flag(sk, SOCK_DEAD))
		sk_wake_async(sk, 0, POLL_ERR);
	dccp_time_wait(sk, DCCP_TIME_WAIT, 0);
}

static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
{
	struct dccp_sock *dp = dccp_sk(sk);

	if (dccp_msk(sk)->dccpms_send_ack_vector)
		dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
					    DCCP_SKB_CB(skb)->dccpd_ack_seq);
}

static int dccp_check_seqno(struct sock *sk, struct sk_buff *skb)
{
	const struct dccp_hdr *dh = dccp_hdr(skb);
	struct dccp_sock *dp = dccp_sk(sk);
	u64 lswl, lawl, seqno = DCCP_SKB_CB(skb)->dccpd_seq,
			ackno = DCCP_SKB_CB(skb)->dccpd_ack_seq;

	/*
	 *   Step 5: Prepare sequence numbers for Sync
	 *     If P.type == Sync or P.type == SyncAck,
	 *	  If S.AWL <= P.ackno <= S.AWH and P.seqno >= S.SWL,
	 *	     / * P is valid, so update sequence number variables
	 *		 accordingly.  After this update, P will pass the tests
	 *		 in Step 6.  A SyncAck is generated if necessary in
	 *		 Step 15 * /
	 *	     Update S.GSR, S.SWL, S.SWH
	 *	  Otherwise,
	 *	     Drop packet and return
	 */
	if (dh->dccph_type == DCCP_PKT_SYNC ||
	    dh->dccph_type == DCCP_PKT_SYNCACK) {
		if (between48(ackno, dp->dccps_awl, dp->dccps_awh) &&
		    dccp_delta_seqno(dp->dccps_swl, seqno) >= 0)
			dccp_update_gsr(sk, seqno);
		else
			return -1;
	}

	/*
	 *   Step 6: Check sequence numbers
	 *      Let LSWL = S.SWL and LAWL = S.AWL
	 *      If P.type == CloseReq or P.type == Close or P.type == Reset,
	 *	  LSWL := S.GSR + 1, LAWL := S.GAR
	 *      If LSWL <= P.seqno <= S.SWH
	 *	     and (P.ackno does not exist or LAWL <= P.ackno <= S.AWH),
	 *	  Update S.GSR, S.SWL, S.SWH
	 *	  If P.type != Sync,
	 *	     Update S.GAR
	 */
	lswl = dp->dccps_swl;
	lawl = dp->dccps_awl;

	if (dh->dccph_type == DCCP_PKT_CLOSEREQ ||
	    dh->dccph_type == DCCP_PKT_CLOSE ||
	    dh->dccph_type == DCCP_PKT_RESET) {
		lswl = ADD48(dp->dccps_gsr, 1);
		lawl = dp->dccps_gar;
	}

	if (between48(seqno, lswl, dp->dccps_swh) &&
	    (ackno == DCCP_PKT_WITHOUT_ACK_SEQ ||
	     between48(ackno, lawl, dp->dccps_awh))) {
		dccp_update_gsr(sk, seqno);

		if (dh->dccph_type != DCCP_PKT_SYNC &&
		    (ackno != DCCP_PKT_WITHOUT_ACK_SEQ))
			dp->dccps_gar = ackno;
	} else {
		unsigned long now = jiffies;
		/*
		 *   Step 6: Check sequence numbers
		 *      Otherwise,
		 *         If P.type == Reset,
		 *            Send Sync packet acknowledging S.GSR
		 *         Otherwise,
		 *            Send Sync packet acknowledging P.seqno
		 *      Drop packet and return
		 *
		 *   These Syncs are rate-limited as per RFC 4340, 7.5.4:
		 *   at most 1 / (dccp_sync_rate_limit * HZ) Syncs per second.
		 */
		if (time_before(now, (dp->dccps_rate_last +
				      sysctl_dccp_sync_ratelimit)))
			return 0;

		DCCP_WARN("DCCP: Step 6 failed for %s packet, "
			  "(LSWL(%llu) <= P.seqno(%llu) <= S.SWH(%llu)) and "
			  "(P.ackno %s or LAWL(%llu) <= P.ackno(%llu) <= S.AWH(%llu), "
			  "sending SYNC...\n",  dccp_packet_name(dh->dccph_type),
			  (unsigned long long) lswl, (unsigned long long) seqno,
			  (unsigned long long) dp->dccps_swh,
			  (ackno == DCCP_PKT_WITHOUT_ACK_SEQ) ? "doesn't exist"
							      : "exists",
			  (unsigned long long) lawl, (unsigned long long) ackno,
			  (unsigned long long) dp->dccps_awh);

		dp->dccps_rate_last = now;

		if (dh->dccph_type == DCCP_PKT_RESET)
			seqno = dp->dccps_gsr;
		dccp_send_sync(sk, seqno, DCCP_PKT_SYNC);
		return -1;
	}

	return 0;
}

static int __dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
				  const struct dccp_hdr *dh, const unsigned len)
{
	struct dccp_sock *dp = dccp_sk(sk);

	switch (dccp_hdr(skb)->dccph_type) {
	case DCCP_PKT_DATAACK:
	case DCCP_PKT_DATA:
		/*
		 * FIXME: check if sk_receive_queue is full, schedule DATA_DROPPED
		 * option if it is.
		 */
		__skb_pull(skb, dh->dccph_doff * 4);
		__skb_queue_tail(&sk->sk_receive_queue, skb);
		skb_set_owner_r(skb, sk);
		sk->sk_data_ready(sk, 0);
		return 0;
	case DCCP_PKT_ACK:
		goto discard;
	case DCCP_PKT_RESET:
		/*
		 *  Step 9: Process Reset
		 *	If P.type == Reset,
		 *		Tear down connection
		 *		S.state := TIMEWAIT
		 *		Set TIMEWAIT timer
		 *		Drop packet and return
		 */
		dccp_rcv_reset(sk, skb);
		return 0;
	case DCCP_PKT_CLOSEREQ:
		dccp_rcv_closereq(sk, skb);
		goto discard;
	case DCCP_PKT_CLOSE:
		dccp_rcv_close(sk, skb);
		return 0;
	case DCCP_PKT_REQUEST:
		/* Step 7
		 *   or (S.is_server and P.type == Response)
		 *   or (S.is_client and P.type == Request)
		 *   or (S.state >= OPEN and P.type == Request
		 *	and P.seqno >= S.OSR)
		 *    or (S.state >= OPEN and P.type == Response
		 *	and P.seqno >= S.OSR)
		 *    or (S.state == RESPOND and P.type == Data),
		 *  Send Sync packet acknowledging P.seqno
		 *  Drop packet and return
		 */
		if (dp->dccps_role != DCCP_ROLE_LISTEN)
			goto send_sync;
		goto check_seq;
	case DCCP_PKT_RESPONSE:
		if (dp->dccps_role != DCCP_ROLE_CLIENT)
			goto send_sync;
check_seq:
		if (dccp_delta_seqno(dp->dccps_osr,
				     DCCP_SKB_CB(skb)->dccpd_seq) >= 0) {
send_sync:
			dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
				       DCCP_PKT_SYNC);
		}
		break;
	case DCCP_PKT_SYNC:
		dccp_send_sync(sk, DCCP_SKB_CB(skb)->dccpd_seq,
			       DCCP_PKT_SYNCACK);
		/*
		 * From RFC 4340, sec. 5.7
		 *
		 * As with DCCP-Ack packets, DCCP-Sync and DCCP-SyncAck packets
		 * MAY have non-zero-length application data areas, whose
		 * contents receivers MUST ignore.
		 */
		goto discard;
	}

	DCCP_INC_STATS_BH(DCCP_MIB_INERRS);
discard:
	__kfree_skb(skb);
	return 0;
}

int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
			 const struct dccp_hdr *dh, const unsigned len)
{
	struct dccp_sock *dp = dccp_sk(sk);

	if (dccp_check_seqno(sk, skb))
		goto discard;

	if (dccp_parse_options(sk, skb))
		goto discard;

	if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
		dccp_event_ack_recv(sk, skb);

	if (dccp_msk(sk)->dccpms_send_ack_vector &&
	    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
			    DCCP_SKB_CB(skb)->dccpd_seq,
			    DCCP_ACKVEC_STATE_RECEIVED))
		goto discard;

	ccid_hc_rx_packet_recv(dp->dccps_hc_rx_ccid, sk, skb);
	ccid_hc_tx_packet_recv(dp->dccps_hc_tx_ccid, sk, skb);

	return __dccp_rcv_established(sk, skb, dh, len);
discard:
	__kfree_skb(skb);
	return 0;
}

EXPORT_SYMBOL_GPL(dccp_rcv_established);

static int dccp_rcv_request_sent_state_process(struct sock *sk,
					       struct sk_buff *skb,
					       const struct dccp_hdr *dh,
					       const unsigned len)
{
	/*
	 *  Step 4: Prepare sequence numbers in REQUEST
	 *     If S.state == REQUEST,
	 *	  If (P.type == Response or P.type == Reset)
	 *		and S.AWL <= P.ackno <= S.AWH,
	 *	     / * Set sequence number variables corresponding to the
	 *		other endpoint, so P will pass the tests in Step 6 * /
	 *	     Set S.GSR, S.ISR, S.SWL, S.SWH
	 *	     / * Response processing continues in Step 10; Reset