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![Eric Dumazet](/assets/img/avatar_default.png)
Multiple cpus can process duplicates of incoming ACK messages matching a SYN_RECV request socket. This is a rare event under normal operations, but definitely can happen. Only one must win the race, otherwise corruption would occur. To fix this without adding new atomic ops, we use logic in inet_ehash_nolisten() to detect the request was present in the same ehash bucket where we try to insert the new child. If request socket was not found, we have to undo the child creation. This actually removes a spin_lock()/spin_unlock() pair in reqsk_queue_unlink() for the fast path. Fixes:e994b2f0fb
("tcp: do not lock listener to process SYN packets") Fixes:079096f103
("tcp/dccp: install syn_recv requests into ehash table") Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
261 lines
7.1 KiB
C
261 lines
7.1 KiB
C
/*
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* net/dccp/minisocks.c
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*
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* An implementation of the DCCP protocol
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* Arnaldo Carvalho de Melo <acme@conectiva.com.br>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/dccp.h>
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#include <linux/gfp.h>
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#include <linux/kernel.h>
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#include <linux/skbuff.h>
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#include <linux/timer.h>
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#include <net/sock.h>
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#include <net/xfrm.h>
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#include <net/inet_timewait_sock.h>
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#include "ackvec.h"
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#include "ccid.h"
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#include "dccp.h"
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#include "feat.h"
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struct inet_timewait_death_row dccp_death_row = {
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.sysctl_max_tw_buckets = NR_FILE * 2,
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.hashinfo = &dccp_hashinfo,
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};
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EXPORT_SYMBOL_GPL(dccp_death_row);
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void dccp_time_wait(struct sock *sk, int state, int timeo)
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{
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struct inet_timewait_sock *tw;
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tw = inet_twsk_alloc(sk, &dccp_death_row, state);
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if (tw != NULL) {
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const struct inet_connection_sock *icsk = inet_csk(sk);
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const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
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#if IS_ENABLED(CONFIG_IPV6)
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if (tw->tw_family == PF_INET6) {
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tw->tw_v6_daddr = sk->sk_v6_daddr;
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tw->tw_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
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tw->tw_ipv6only = sk->sk_ipv6only;
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}
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#endif
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/* Get the TIME_WAIT timeout firing. */
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if (timeo < rto)
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timeo = rto;
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tw->tw_timeout = DCCP_TIMEWAIT_LEN;
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if (state == DCCP_TIME_WAIT)
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timeo = DCCP_TIMEWAIT_LEN;
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inet_twsk_schedule(tw, timeo);
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/* Linkage updates. */
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__inet_twsk_hashdance(tw, sk, &dccp_hashinfo);
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inet_twsk_put(tw);
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} else {
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/* Sorry, if we're out of memory, just CLOSE this
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* socket up. We've got bigger problems than
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* non-graceful socket closings.
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*/
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DCCP_WARN("time wait bucket table overflow\n");
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}
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dccp_done(sk);
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}
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struct sock *dccp_create_openreq_child(const struct sock *sk,
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const struct request_sock *req,
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const struct sk_buff *skb)
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{
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/*
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* Step 3: Process LISTEN state
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*
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* (* Generate a new socket and switch to that socket *)
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* Set S := new socket for this port pair
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*/
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struct sock *newsk = inet_csk_clone_lock(sk, req, GFP_ATOMIC);
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if (newsk != NULL) {
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struct dccp_request_sock *dreq = dccp_rsk(req);
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struct inet_connection_sock *newicsk = inet_csk(newsk);
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struct dccp_sock *newdp = dccp_sk(newsk);
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newdp->dccps_role = DCCP_ROLE_SERVER;
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newdp->dccps_hc_rx_ackvec = NULL;
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newdp->dccps_service_list = NULL;
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newdp->dccps_service = dreq->dreq_service;
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newdp->dccps_timestamp_echo = dreq->dreq_timestamp_echo;
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newdp->dccps_timestamp_time = dreq->dreq_timestamp_time;
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newicsk->icsk_rto = DCCP_TIMEOUT_INIT;
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INIT_LIST_HEAD(&newdp->dccps_featneg);
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/*
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* Step 3: Process LISTEN state
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*
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* Choose S.ISS (initial seqno) or set from Init Cookies
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* Initialize S.GAR := S.ISS
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* Set S.ISR, S.GSR from packet (or Init Cookies)
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*
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* Setting AWL/AWH and SWL/SWH happens as part of the feature
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* activation below, as these windows all depend on the local
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* and remote Sequence Window feature values (7.5.2).
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*/
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newdp->dccps_iss = dreq->dreq_iss;
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newdp->dccps_gss = dreq->dreq_gss;
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newdp->dccps_gar = newdp->dccps_iss;
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newdp->dccps_isr = dreq->dreq_isr;
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newdp->dccps_gsr = dreq->dreq_gsr;
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/*
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* Activate features: initialise CCIDs, sequence windows etc.
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*/
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if (dccp_feat_activate_values(newsk, &dreq->dreq_featneg)) {
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/* It is still raw copy of parent, so invalidate
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* destructor and make plain sk_free() */
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newsk->sk_destruct = NULL;
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sk_free(newsk);
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return NULL;
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}
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dccp_init_xmit_timers(newsk);
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DCCP_INC_STATS_BH(DCCP_MIB_PASSIVEOPENS);
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}
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return newsk;
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}
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EXPORT_SYMBOL_GPL(dccp_create_openreq_child);
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/*
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* Process an incoming packet for RESPOND sockets represented
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* as an request_sock.
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*/
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struct sock *dccp_check_req(struct sock *sk, struct sk_buff *skb,
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struct request_sock *req)
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{
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struct sock *child = NULL;
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struct dccp_request_sock *dreq = dccp_rsk(req);
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bool own_req;
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/* Check for retransmitted REQUEST */
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if (dccp_hdr(skb)->dccph_type == DCCP_PKT_REQUEST) {
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if (after48(DCCP_SKB_CB(skb)->dccpd_seq, dreq->dreq_gsr)) {
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dccp_pr_debug("Retransmitted REQUEST\n");
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dreq->dreq_gsr = DCCP_SKB_CB(skb)->dccpd_seq;
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/*
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* Send another RESPONSE packet
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* To protect against Request floods, increment retrans
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* counter (backoff, monitored by dccp_response_timer).
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*/
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inet_rtx_syn_ack(sk, req);
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}
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/* Network Duplicate, discard packet */
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return NULL;
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}
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DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
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if (dccp_hdr(skb)->dccph_type != DCCP_PKT_ACK &&
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dccp_hdr(skb)->dccph_type != DCCP_PKT_DATAACK)
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goto drop;
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/* Invalid ACK */
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if (!between48(DCCP_SKB_CB(skb)->dccpd_ack_seq,
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dreq->dreq_iss, dreq->dreq_gss)) {
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dccp_pr_debug("Invalid ACK number: ack_seq=%llu, "
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"dreq_iss=%llu, dreq_gss=%llu\n",
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(unsigned long long)
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DCCP_SKB_CB(skb)->dccpd_ack_seq,
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(unsigned long long) dreq->dreq_iss,
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(unsigned long long) dreq->dreq_gss);
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goto drop;
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}
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if (dccp_parse_options(sk, dreq, skb))
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goto drop;
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child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb, req, NULL,
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req, &own_req);
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if (!child)
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goto listen_overflow;
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return inet_csk_complete_hashdance(sk, child, req, own_req);
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listen_overflow:
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dccp_pr_debug("listen_overflow!\n");
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DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_TOO_BUSY;
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drop:
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if (dccp_hdr(skb)->dccph_type != DCCP_PKT_RESET)
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req->rsk_ops->send_reset(sk, skb);
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inet_csk_reqsk_queue_drop(sk, req);
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return NULL;
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}
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EXPORT_SYMBOL_GPL(dccp_check_req);
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/*
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* Queue segment on the new socket if the new socket is active,
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* otherwise we just shortcircuit this and continue with
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* the new socket.
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*/
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int dccp_child_process(struct sock *parent, struct sock *child,
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struct sk_buff *skb)
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{
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int ret = 0;
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const int state = child->sk_state;
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if (!sock_owned_by_user(child)) {
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ret = dccp_rcv_state_process(child, skb, dccp_hdr(skb),
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skb->len);
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/* Wakeup parent, send SIGIO */
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if (state == DCCP_RESPOND && child->sk_state != state)
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parent->sk_data_ready(parent);
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} else {
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/* Alas, it is possible again, because we do lookup
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* in main socket hash table and lock on listening
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* socket does not protect us more.
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*/
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__sk_add_backlog(child, skb);
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}
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bh_unlock_sock(child);
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sock_put(child);
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return ret;
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}
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EXPORT_SYMBOL_GPL(dccp_child_process);
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void dccp_reqsk_send_ack(const struct sock *sk, struct sk_buff *skb,
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struct request_sock *rsk)
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{
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DCCP_BUG("DCCP-ACK packets are never sent in LISTEN/RESPOND state");
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}
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EXPORT_SYMBOL_GPL(dccp_reqsk_send_ack);
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int dccp_reqsk_init(struct request_sock *req,
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struct dccp_sock const *dp, struct sk_buff const *skb)
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{
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struct dccp_request_sock *dreq = dccp_rsk(req);
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inet_rsk(req)->ir_rmt_port = dccp_hdr(skb)->dccph_sport;
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inet_rsk(req)->ir_num = ntohs(dccp_hdr(skb)->dccph_dport);
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inet_rsk(req)->acked = 0;
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dreq->dreq_timestamp_echo = 0;
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/* inherit feature negotiation options from listening socket */
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return dccp_feat_clone_list(&dp->dccps_featneg, &dreq->dreq_featneg);
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}
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EXPORT_SYMBOL_GPL(dccp_reqsk_init);
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