// SPDX-License-Identifier: GPL-2.0-or-later
/*
* net/dccp/output.c
*
* An implementation of the DCCP protocol
* Arnaldo Carvalho de Melo <[email protected]>
*/
#include <linux/dccp.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <net/inet_sock.h>
#include <net/sock.h>
#include "ackvec.h"
#include "ccid.h"
#include "dccp.h"
static inline void dccp_event_ack_sent(struct sock *sk)
{
inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
}
/* enqueue @skb on sk_send_head for retransmission, return clone to send now */
static struct sk_buff *dccp_skb_entail(struct sock *sk, struct sk_buff *skb)
{
skb_set_owner_w(skb, sk);
WARN_ON(sk->sk_send_head);
sk->sk_send_head = skb;
return skb_clone(sk->sk_send_head, gfp_any());
}
/*
* All SKB's seen here are completely headerless. It is our
* job to build the DCCP header, and pass the packet down to
* IP so it can do the same plus pass the packet off to the
* device.
*/
static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb)
{
if (likely(skb != NULL)) {
struct inet_sock *inet = inet_sk(sk);
const struct inet_connection_sock *icsk = inet_csk(sk);
struct dccp_sock *dp = dccp_sk(sk);
struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb);
struct dccp_hdr *dh;
/* XXX For now we're using only 48 bits sequence numbers */
const u32 dccp_header_size = sizeof(*dh) +
sizeof(struct dccp_hdr_ext) +
dccp_packet_hdr_len(dcb->dccpd_type);
int err, set_ack = 1;
u64 ackno = dp->dccps_gsr;
/*
* Increment GSS here already in case the option code needs it.
* Update GSS for real only if option processing below succeeds.
*/
dcb->dccpd_seq = ADD48(dp->dccps_gss, 1);
switch (dcb->dccpd_type) {
case DCCP_PKT_DATA:
set_ack = 0;
fallthrough;
case DCCP_PKT_DATAACK:
case DCCP_PKT_RESET:
break;
case DCCP_PKT_REQUEST:
set_ack = 0;
/* Use ISS on the first (non-retransmitted) Request. */
if (icsk->icsk_retransmits == 0)
dcb->dccpd_seq = dp->dccps_iss;
fallthrough;
case DCCP_PKT_SYNC:
case DCCP_PKT_SYNCACK:
ackno = dcb->dccpd_ack_seq;
fallthrough;
default:
/*
* Set owner/destructor: some skbs are allocated via
* alloc_skb (e.g. when retransmission may happen).
* Only Data, DataAck, and Reset packets should come
* through here with skb->sk set.
*/
WARN_ON(skb->sk);
skb_set_owner_w(skb, sk);
break;
}
if (dccp_insert_options(sk, skb)) {
kfree_skb(skb);
return -EPROTO;
}
/* Build DCCP header and checksum it. */
dh = dccp_zeroed_hdr(skb, dccp_header_size);
dh->dccph_type = dcb->dccpd_type;
dh->dccph_sport = inet->inet_sport;
dh->dccph_dport = inet->inet_dport;
dh->dccph_doff = (dccp_header_size + dcb->dccpd_opt_len) / 4;
dh->dccph_ccval = dcb->dccpd_ccval;
dh->dccph_cscov = dp->dccps_pcslen;
/* XXX For now we're using only 48 bits sequence numbers */
dh->dccph_x = 1;
dccp_update_gss(sk, dcb->dccpd_seq);
dccp_hdr_set_seq(dh, dp->dccps_gss);
if (set_ack)
dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno);
switch (dcb->dccpd_type) {
case DCCP_PKT_REQUEST:
dccp_hdr_request(skb)->dccph_req_service =
dp->dccps_service;
/*
* Limit Ack window to ISS <= P.ackno <= GSS, so that
* only Responses to Requests we sent are considered.
*/
dp->dccps_awl = dp->dccps_iss;
break;
case DCCP_PKT_RESET:
dccp_hdr_reset(skb)->dccph_reset_code =
dcb->dccpd_reset_code;
break;
}
icsk->icsk_af_ops->send_check(sk, skb);
if (set_ack)
dccp_event_ack_sent(sk);
DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl);
return net_xmit_eval(err);
}
return -ENOBUFS;
}
/**
* dccp_determine_ccmps - Find out about CCID-specific packet-size limits
* @dp: socket to find packet size limits of
*
* We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.),
* since the RX CCID is restricted to feedback packets (Acks), which are small
* in comparison with the data traffic. A value of 0 means "no current CCMPS".
*/
static u32 dccp_determine_ccmps(const struct dccp_sock *dp)
{
const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid;
if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL)
return 0;
return tx_ccid->ccid_ops->ccid_ccmps;
}
unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct dccp_sock *dp = dccp_sk(sk);
u32 ccmps = dccp_determine_ccmps(dp);
u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu;
/* Account for header lengths and IPv4/v6 option overhead */
cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len +
sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext));
/*
* Leave enough headroom for common DCCP header options.
* This only considers options which may appear on DCCP-Data packets, as
* per table 3 in RFC 4340, 5.8. When running out of space for other
* options (eg. Ack Vector which can take up to 255 bytes), it is better
* to schedule a separate Ack. Thus we leave headroom for the following:
* - 1 byte for Slow Receiver (11.6)
* - 6 bytes for Timestamp (13.1)
* - 10 bytes for Timestamp Echo (13.3)
* - 8 bytes for NDP count (7.7, when activated)
* - 6 bytes for Data Checksum (9.3)
* - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled)
*/
cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 +
(dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4);
/* And store cached results */
icsk->icsk_pmtu_cookie = pmtu;
WRITE_ONCE(dp->dccps_mss_cache, cur_mps);
return cur_mps;
}
EXPORT_SYMBOL_GPL(dccp_sync_mss);
void dccp_write_space(struct sock *sk)
{
struct socket_wq *wq;
rcu_read_lock();
wq = rcu_dereference(sk->sk_wq);
if (skwq_has_sleeper(wq))
wake_up_interruptible(&wq->wait);
/* Should agree with poll, otherwise some programs break */
if (sock_writeable(sk))
sk_wake_async_rcu(sk, SOCK_WAKE_SPACE, POLL_OUT);
rcu_read_unlock();
}
/**
* dccp_wait_for_ccid - Await CCID send permission
* @sk: socket to wait for
* @delay: timeout in jiffies
*
* This is used by CCIDs which need to delay the send time in process context.
*/
static int dccp_wait_for_ccid(struct sock *sk, unsigned long delay)
{
DEFINE_WAIT(wait);
long remaining;
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
sk->sk_write_pending++;
release_sock(sk);
remaining = schedule_timeout(delay);
lock_sock(sk);
sk->sk_write_pending--;
finish_wait(sk_sleep(sk), &wait);
if (signal_pending(current) || sk->sk_err)
return -1;
return remaining;
}
/**
* dccp_xmit_packet - Send data packet under control of CCID
* @sk: socket to send data packet on
*
* Transmits next-queued payload and informs CCID to account for the packet.
*/
static void dccp_xmit_packet(struct sock *sk)
{
int err, len;
struct dccp_sock *dp = dccp_sk(sk);
struct sk_buff *skb = dccp_qpolicy_pop(sk);
if (unlikely(skb == NULL))
return;
len = skb->len;
if (sk->sk_state == DCCP_PARTOPEN) {
const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD;
/*
* See 8.1.5 - Handshake Completion.
*
* For robustness we resend Confirm options until the client has
* entered OPEN. During the initial feature negotiation, the MPS
* is smaller than usual, reduced by the Change/Confirm options.
*/
if (!list_empty(&dp->dccps_featneg) && len > cur_mps) {
DCCP_WARN("Payload too large (%d) for featneg.\n", len);
dccp_send_ack(sk);
dccp_feat_list_purge(&dp->dccps_featneg);
}
inet_csk_schedule_ack(sk);
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
inet_csk(sk)->icsk_rto,
DCCP_RTO_MAX);
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
} else if (dccp_ack_pending(sk)) {
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK;
} else {
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA;
}
err = dccp_transmit_skb(sk, skb);
if (err)
dccp_pr_debug("transmit_skb() returned err=%d\n", err);
/*
* Register this one as sent even if an error occurred. To the remote
* end a local packet drop is indistinguishable from network loss, i.e.
* any local drop will eventually be reported via receiver feedback.
*/
ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len);
/*
* If the CCID needs to transfer additional header options out-of-band
* (e.g. Ack Vectors or feature-negotiation options), it activates this
* flag to schedule a Sync. The Sync will automatically incorporate all
* currently pending header options, thus clearing the backlog.
*/
if (dp->dccps_sync_scheduled)
dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC);
}
/**
* dccp_flush_write_queue - Drain queue at end of connection
* @sk: socket to be drained
* @time_budget: time allowed to drain the queue
*
* Since dccp_sendmsg queues packets without waiting for them to be sent, it may
* happen that the TX queue is not empty at the end of a connection. We give the
* HC-sender CCID a grace period of up to @time_budget jiffies. If this function
* returns with a non-empty write queue, it will be purged later.
*/
void dccp_flush_write_queue(struct sock *sk, long *time_budget)
{
struct dccp_sock *dp = dccp_sk(sk);
struct sk_buff *skb;
long delay, rc;
while (*time_budget > 0 && (skb = skb_peek(&sk->sk_write_queue))) {
rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
switch (ccid_packet_dequeue_eval(rc)) {
case CCID_PACKET_WILL_DEQUEUE_LATER:
/*
* If the CCID determines when to send, the next sending
* time is unknown or the CCID may not even send again
* (e.g. remote host crashes or lost Ack packets).
*/
DCCP_WARN("CCID did not manage to send all packets\n");
return;
case CCID_PACKET_DELAY:
delay = msecs_to_jiffies(rc);
if (delay > *time_budget)
return;
rc = dccp_wait_for_ccid(sk, delay);
if (rc < 0)
return;
*time_budget -= (delay - rc);
/* check again if we can send now */
break;
case CCID_PACKET_SEND_AT_ONCE:
dccp_xmit_packet(sk);
break;
case CCID_PACKET_ERR:
skb_dequeue(&sk->sk_write_queue);
kfree_skb(skb);
dccp_pr_debug("packet discarded due to err=%ld\n", rc);
}
}
}
void dccp_write_xmit(struct sock *sk)
{
struct dccp_sock *dp = dccp_sk(sk);
struct sk_buff *skb;
while ((skb = dccp_qpolicy_top(sk))) {
int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb);
switch (ccid_packet_dequeue_eval(rc)) {
case CCID_PACKET_WILL_DEQUEUE_LATER:
return;
case CCID_PACKET_DELAY:
sk_reset_timer(sk, &dp->dccps_xmit_timer,
jiffies + msecs_to_jiffies(rc));
return;
case CCID_PACKET_SEND_AT_ONCE:
dccp_xmit_packet(sk);
break;
case CCID_PACKET_ERR:
dccp_qpolicy_drop(sk, skb);
dccp_pr_debug("packet discarded due to err=%d\n", rc);
}
}
}
/**
* dccp_retransmit_skb - Retransmit Request, Close, or CloseReq packets
* @sk: socket to perform retransmit on
*
* There are only four retransmittable packet types in DCCP:
* - Request in client-REQUEST state (sec. 8.1.1),
* - CloseReq in server-CLOSEREQ state (sec. 8.3),
* - Close in node-CLOSING state (sec. 8.3),
* - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()).
* This function expects sk->sk_send_head to contain the original skb.
*/
int dccp_retransmit_skb(struct sock *sk)
{
WARN_ON(sk->sk_send_head == NULL);
if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0)
return -EHOSTUNREACH; /* Routing failure or similar. */
/* this count is used to distinguish original and retransmitted skb */
inet_csk(sk)->icsk_retransmits++;
return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC));
}
struct sk_buff *dccp_make_response(const struct sock *sk, struct dst_entry *dst,
struct request_sock *req)
{
struct dccp_hdr *dh;
struct dccp_request_sock *dreq;
const u32 dccp_header_size = sizeof(struct dccp_hdr) +
sizeof(struct dccp_hdr_ext) +
sizeof(struct dccp_hdr_response);
struct sk_buff *skb;
/* sk is marked const to clearly express we dont hold socket lock.
* sock_wmalloc() will atomically change sk->sk_wmem_alloc,
* it is safe to promote sk to non const.
*/
skb = sock_wmalloc((struct sock *)sk, MAX_DCCP_HEADER, 1,
GFP_ATOMIC);
if (!skb)
return NULL;
skb_reserve(skb, MAX_DCCP_HEADER);
skb_dst_set(skb, dst_clone(dst));
dreq = dccp_rsk(req);
if (inet_rsk(req)->acked) /* increase GSS upon retransmission */
dccp_inc_seqno(&dreq->dreq_gss);
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
DCCP_SKB_CB(skb)->dccpd_seq = dreq->dreq_gss;
/* Resolve feature dependencies resulting from choice of CCID */
if (dccp_feat_server_ccid_dependencies(dreq))
goto response_failed;
if (dccp_insert_options_rsk(dreq, skb))
goto response_failed;
/* Build and checksum header */
dh = dccp_zeroed_hdr(skb, dccp_header_size);
dh->dccph_sport = htons(inet_rsk(req)->ir_num);
dh->dccph_dport = inet_rsk(req)->ir_rmt_port;
dh->dccph_doff = (dccp_header_size +
DCCP_SKB_CB(skb)->dccpd_opt_len) / 4;
dh->dccph_type = DCCP_PKT_RESPONSE;
dh->dccph_x = 1;
dccp_hdr_set_seq(dh, dreq->dreq_gss);
dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr);
dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service;
dccp_csum_outgoing(skb);
/* We use `acked' to remember that a Response was already sent. */
inet_rsk(req)->acked = 1;
DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
return skb;
response_failed:
kfree_skb(skb);
return NULL;
}
EXPORT_SYMBOL_GPL(dccp_make_response);
/* answer offending packet in @rcv_skb with Reset from control socket @ctl */
struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb)
{
struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh;
struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb);
const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) +
sizeof(struct dccp_hdr_ext) +
sizeof(struct dccp_hdr_reset);
struct dccp_hdr_reset *dhr;
struct sk_buff *skb;
skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
if (skb == NULL)
return NULL;
skb_reserve(skb, sk->sk_prot->max_header);
/* Swap the send and the receive. */
dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len);
dh->dccph_type = DCCP_PKT_RESET;
dh->dccph_sport = rxdh->dccph_dport;
dh->dccph_dport = rxdh->dccph_sport;
dh->dccph_doff = dccp_hdr_reset_len / 4;
dh->dccph_x = 1;
dhr = dccp_hdr_reset(skb);
dhr->dccph_reset_code = dcb->dccpd_reset_code;
switch (dcb->dccpd_reset_code) {
case DCCP_RESET_CODE_PACKET_ERROR:
dhr->dccph_reset_data[0] = rxdh->dccph_type;
break;
case DCCP_RESET_CODE_OPTION_ERROR:
case DCCP_RESET_CODE_MANDATORY_ERROR:
memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3);
break;
}
/*
* From RFC 4340, 8.3.1:
* If P.ackno exists, set R.seqno := P.ackno + 1.
* Else set R.seqno := 0.
*/
if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1));
dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq);
dccp_csum_outgoing(skb);
return skb;
}
EXPORT_SYMBOL_GPL(dccp_ctl_make_reset);
/* send Reset on established socket, to close or abort the connection */
int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code)
{
struct sk_buff *skb;
/*
* FIXME: what if rebuild_header fails?
* Should we be doing a rebuild_header here?
*/
int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk);
if (err != 0)
return err;
skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC);
if (skb == NULL)
return -ENOBUFS;
/* Reserve space for headers and prepare control bits. */
skb_reserve(skb, sk->sk_prot->max_header);
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESET;
DCCP_SKB_CB(skb)->dccpd_reset_code = code;
return dccp_transmit_skb(sk, skb);
}
/*
* Do all connect socket setups that can be done AF independent.
*/
int dccp_connect(struct sock *sk)
{
struct sk_buff *skb;
struct dccp_sock *dp = dccp_sk(sk);
struct dst_entry *dst = __sk_dst_get(sk);
struct inet_connection_sock *icsk = inet_csk(sk);
sk->sk_err = 0;
sock_reset_flag(sk, SOCK_DONE);
dccp_sync_mss(sk, dst_mtu(dst));
/* do not connect if feature negotiation setup fails */
if (dccp_feat_finalise_settings(dccp_sk(sk)))
return -EPROTO;
/* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */
dp->dccps_gar = dp->dccps_iss;
skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
if (unlikely(skb == NULL))
return -ENOBUFS;
/* Reserve space for headers. */
skb_reserve(skb, sk->sk_prot->max_header);
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST;
dccp_transmit_skb(sk, dccp_skb_entail(sk, skb));
DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS);
/* Timer for repeating the REQUEST until an answer. */
icsk->icsk_retransmits = 0;
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
icsk->icsk_rto, DCCP_RTO_MAX);
return 0;
}
EXPORT_SYMBOL_GPL(dccp_connect);
void dccp_send_ack(struct sock *sk)
{
/* If we have been reset, we may not send again. */
if (sk->sk_state != DCCP_CLOSED) {
struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header,
GFP_ATOMIC);
if (skb == NULL) {
inet_csk_schedule_ack(sk);
inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
TCP_DELACK_MAX,
DCCP_RTO_MAX);
return;
}
/* Reserve space for headers */
skb_reserve(skb, sk->sk_prot->max_header);
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK;
dccp_transmit_skb(sk, skb);
}
}
EXPORT_SYMBOL_GPL(dccp_send_ack);
#if 0
/* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */
void dccp_send_delayed_ack(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
/*
* FIXME: tune this timer. elapsed time fixes the skew, so no problem
* with using 2s, and active senders also piggyback the ACK into a
* DATAACK packet, so this is really for quiescent senders.
*/
unsigned long timeout = jiffies + 2 * HZ;
/* Use new timeout only if there wasn't a older one earlier. */
if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
/* If delack timer was blocked or is about to expire,
* send ACK now.
*
* FIXME: check the "about to expire" part
*/
if (icsk->icsk_ack.blocked) {
dccp_send_ack(sk);
return;
}
if (!time_before(timeout, icsk->icsk_ack.timeout))
timeout = icsk->icsk_ack.timeout;
}
icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
icsk->icsk_ack.timeout = timeout;
sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
}
#endif
void dccp_send_sync(struct sock *sk, const u64 ackno,
const enum dccp_pkt_type pkt_type)
{
/*
* We are not putting this on the write queue, so
* dccp_transmit_skb() will set the ownership to this
* sock.
*/
struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC);
if (skb == NULL) {
/* FIXME: how to make sure the sync is sent? */
DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type));
return;
}
/* Reserve space for headers and prepare control bits. */
skb_reserve(skb, sk->sk_prot->max_header);
DCCP_SKB_CB(skb)->dccpd_type = pkt_type;
DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno;
/*
* Clear the flag in case the Sync was scheduled for out-of-band data,
* such as carrying a long Ack Vector.
*/
dccp_sk(sk)->dccps_sync_scheduled = 0;
dccp_transmit_skb(sk, skb);
}
EXPORT_SYMBOL_GPL(dccp_send_sync);
/*
* Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This
* cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under
* any circumstances.
*/
void dccp_send_close(struct sock *sk, const int active)
{
struct dccp_sock *dp = dccp_sk(sk);
struct sk_buff *skb;
const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC;
skb = alloc_skb(sk->sk_prot->max_header, prio);
if (skb == NULL)
return;
/* Reserve space for headers and prepare control bits. */
skb_reserve(skb, sk->sk_prot->max_header);
if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait)
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ;
else
DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE;
if (active) {
skb = dccp_skb_entail(sk, skb);
/*
* Retransmission timer for active-close: RFC 4340, 8.3 requires
* to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ
* state can be left. The initial timeout is 2 RTTs.
* Since RTT measurement is done by the CCIDs, there is no easy
* way to get an RTT sample. The fallback RTT from RFC 4340, 3.4
* is too low (200ms); we use a high value to avoid unnecessary
* retransmissions when the link RTT is > 0.2 seconds.
* FIXME: Let main module sample RTTs and use that instead.
*/
inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
DCCP_TIMEOUT_INIT, DCCP_RTO_MAX);
}
dccp_transmit_skb(sk, skb);
}
Codebase Browser
linux