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freebsd-skq/sys/netinet/tcp_timewait.c
glebius e35d543ec1 Listening sockets improvements. 
o Separate fields of struct socket that belong to listening from
  fields that belong to normal dataflow, and unionize them.  This
  shrinks the structure a bit.
  - Take out selinfo's from the socket buffers into the socket. The
    first reason is to support braindamaged scenario when a socket is
    added to kevent(2) and then listen(2) is cast on it. The second
    reason is that there is future plan to make socket buffers pluggable,
    so that for a dataflow socket a socket buffer can be changed, and
    in this case we also want to keep same selinfos through the lifetime
    of a socket.
  - Remove struct struct so_accf. Since now listening stuff no longer
    affects struct socket size, just move its fields into listening part
    of the union.
  - Provide sol_upcall field and enforce that so_upcall_set() may be called
    only on a dataflow socket, which has buffers, and for listening sockets
    provide solisten_upcall_set().

o Remove ACCEPT_LOCK() global.
  - Add a mutex to socket, to be used instead of socket buffer lock to lock
    fields of struct socket that don't belong to a socket buffer.
  - Allow to acquire two socket locks, but the first one must belong to a
    listening socket.
  - Make soref()/sorele() to use atomic(9).  This allows in some situations
    to do soref() without owning socket lock.  There is place for improvement
    here, it is possible to make sorele() also to lock optionally.
  - Most protocols aren't touched by this change, except UNIX local sockets.
    See below for more information.

o Reduce copy-and-paste in kernel modules that accept connections from
  listening sockets: provide function solisten_dequeue(), and use it in
  the following modules: ctl(4), iscsi(4), ng_btsocket(4), ng_ksocket(4),
  infiniband, rpc.

o UNIX local sockets.
  - Removal of ACCEPT_LOCK() global uncovered several races in the UNIX
    local sockets.  Most races exist around spawning a new socket, when we
    are connecting to a local listening socket.  To cover them, we need to
    hold locks on both PCBs when spawning a third one.  This means holding
    them across sonewconn().  This creates a LOR between pcb locks and
    unp_list_lock.
  - To fix the new LOR, abandon the global unp_list_lock in favor of global
    unp_link_lock.  Indeed, separating these two locks didn't provide us any
    extra parralelism in the UNIX sockets.
  - Now call into uipc_attach() may happen with unp_link_lock hold if, we
    are accepting, or without unp_link_lock in case if we are just creating
    a socket.
  - Another problem in UNIX sockets is that uipc_close() basicly did nothing
    for a listening socket.  The vnode remained opened for connections.  This
    is fixed by removing vnode in uipc_close().  Maybe the right way would be
    to do it for all sockets (not only listening), simply move the vnode
    teardown from uipc_detach() to uipc_close()?

Sponsored by:		Netflix
Differential Revision:	https://reviews.freebsd.org/D9770
2017-06-08 21:30:34 +00:00

740 lines
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/*-
* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_tcpdebug.h"
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/callout.h>
#include <sys/kernel.h>
#include <sys/sysctl.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/random.h>
#include <vm/uma.h>
#include <net/route.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/vnet.h>
#include <netinet/in.h>
#include <netinet/in_pcb.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/ip_var.h>
#ifdef INET6
#include <netinet/ip6.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/ip6_var.h>
#include <netinet6/scope6_var.h>
#include <netinet6/nd6.h>
#endif
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#ifdef INET6
#include <netinet6/tcp6_var.h>
#endif
#include <netinet/tcpip.h>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif
#ifdef INET6
#include <netinet6/ip6protosw.h>
#endif
#include <machine/in_cksum.h>
#include <security/mac/mac_framework.h>
static VNET_DEFINE(uma_zone_t, tcptw_zone);
#define V_tcptw_zone VNET(tcptw_zone)
static int maxtcptw;
/*
* The timed wait queue contains references to each of the TCP sessions
* currently in the TIME_WAIT state. The queue pointers, including the
* queue pointers in each tcptw structure, are protected using the global
* timewait lock, which must be held over queue iteration and modification.
*
* Rules on tcptw usage:
* - a inpcb is always freed _after_ its tcptw
* - a tcptw relies on its inpcb reference counting for memory stability
* - a tcptw is dereferenceable only while its inpcb is locked
*/
static VNET_DEFINE(TAILQ_HEAD(, tcptw), twq_2msl);
#define V_twq_2msl VNET(twq_2msl)
/* Global timewait lock */
static VNET_DEFINE(struct rwlock, tw_lock);
#define V_tw_lock VNET(tw_lock)
#define TW_LOCK_INIT(tw, d) rw_init_flags(&(tw), (d), 0)
#define TW_LOCK_DESTROY(tw) rw_destroy(&(tw))
#define TW_RLOCK(tw) rw_rlock(&(tw))
#define TW_WLOCK(tw) rw_wlock(&(tw))
#define TW_RUNLOCK(tw) rw_runlock(&(tw))
#define TW_WUNLOCK(tw) rw_wunlock(&(tw))
#define TW_LOCK_ASSERT(tw) rw_assert(&(tw), RA_LOCKED)
#define TW_RLOCK_ASSERT(tw) rw_assert(&(tw), RA_RLOCKED)
#define TW_WLOCK_ASSERT(tw) rw_assert(&(tw), RA_WLOCKED)
#define TW_UNLOCK_ASSERT(tw) rw_assert(&(tw), RA_UNLOCKED)
static void tcp_tw_2msl_reset(struct tcptw *, int);
static void tcp_tw_2msl_stop(struct tcptw *, int);
static int tcp_twrespond(struct tcptw *, int);
static int
tcptw_auto_size(void)
{
int halfrange;
/*
* Max out at half the ephemeral port range so that TIME_WAIT
* sockets don't tie up too many ephemeral ports.
*/
if (V_ipport_lastauto > V_ipport_firstauto)
halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2;
else
halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2;
/* Protect against goofy port ranges smaller than 32. */
return (imin(imax(halfrange, 32), maxsockets / 5));
}
static int
sysctl_maxtcptw(SYSCTL_HANDLER_ARGS)
{
int error, new;
if (maxtcptw == 0)
new = tcptw_auto_size();
else
new = maxtcptw;
error = sysctl_handle_int(oidp, &new, 0, req);
if (error == 0 && req->newptr)
if (new >= 32) {
maxtcptw = new;
uma_zone_set_max(V_tcptw_zone, maxtcptw);
}
return (error);
}
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW,
&maxtcptw, 0, sysctl_maxtcptw, "IU",
"Maximum number of compressed TCP TIME_WAIT entries");
VNET_DEFINE(int, nolocaltimewait) = 0;
#define V_nolocaltimewait VNET(nolocaltimewait)
SYSCTL_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_VNET | CTLFLAG_RW,
&VNET_NAME(nolocaltimewait), 0,
"Do not create compressed TCP TIME_WAIT entries for local connections");
void
tcp_tw_zone_change(void)
{
if (maxtcptw == 0)
uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
}
void
tcp_tw_init(void)
{
V_tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, 0);
TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw);
if (maxtcptw == 0)
uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
else
uma_zone_set_max(V_tcptw_zone, maxtcptw);
TAILQ_INIT(&V_twq_2msl);
TW_LOCK_INIT(V_tw_lock, "tcptw");
}
#ifdef VIMAGE
void
tcp_tw_destroy(void)
{
struct tcptw *tw;
INP_INFO_RLOCK(&V_tcbinfo);
while ((tw = TAILQ_FIRST(&V_twq_2msl)) != NULL)
tcp_twclose(tw, 0);
INP_INFO_RUNLOCK(&V_tcbinfo);
TW_LOCK_DESTROY(V_tw_lock);
uma_zdestroy(V_tcptw_zone);
}
#endif
/*
* Move a TCP connection into TIME_WAIT state.
* tcbinfo is locked.
* inp is locked, and is unlocked before returning.
*/
void
tcp_twstart(struct tcpcb *tp)
{
struct tcptw *tw;
struct inpcb *inp = tp->t_inpcb;
int acknow;
struct socket *so;
#ifdef INET6
int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
#endif
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(inp);
/* A dropped inp should never transition to TIME_WAIT state. */
KASSERT((inp->inp_flags & INP_DROPPED) == 0, ("tcp_twstart: "
"(inp->inp_flags & INP_DROPPED) != 0"));
if (V_nolocaltimewait) {
int error = 0;
#ifdef INET6
if (isipv6)
error = in6_localaddr(&inp->in6p_faddr);
#endif
#if defined(INET6) && defined(INET)
else
#endif
#ifdef INET
error = in_localip(inp->inp_faddr);
#endif
if (error) {
tp = tcp_close(tp);
if (tp != NULL)
INP_WUNLOCK(inp);
return;
}
}
/*
* For use only by DTrace. We do not reference the state
* after this point so modifying it in place is not a problem.
*/
tcp_state_change(tp, TCPS_TIME_WAIT);
tw = uma_zalloc(V_tcptw_zone, M_NOWAIT);
if (tw == NULL) {
/*
* Reached limit on total number of TIMEWAIT connections
* allowed. Remove a connection from TIMEWAIT queue in LRU
* fashion to make room for this connection.
*
* XXX: Check if it possible to always have enough room
* in advance based on guarantees provided by uma_zalloc().
*/
tw = tcp_tw_2msl_scan(1);
if (tw == NULL) {
tp = tcp_close(tp);
if (tp != NULL)
INP_WUNLOCK(inp);
return;
}
}
/*
* The tcptw will hold a reference on its inpcb until tcp_twclose
* is called
*/
tw->tw_inpcb = inp;
in_pcbref(inp); /* Reference from tw */
/*
* Recover last window size sent.
*/
if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
else
tw->last_win = 0;
/*
* Set t_recent if timestamps are used on the connection.
*/
if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
(TF_REQ_TSTMP|TF_RCVD_TSTMP)) {
tw->t_recent = tp->ts_recent;
tw->ts_offset = tp->ts_offset;
} else {
tw->t_recent = 0;
tw->ts_offset = 0;
}
tw->snd_nxt = tp->snd_nxt;
tw->rcv_nxt = tp->rcv_nxt;
tw->iss = tp->iss;
tw->irs = tp->irs;
tw->t_starttime = tp->t_starttime;
tw->tw_time = 0;
/* XXX
* If this code will
* be used for fin-wait-2 state also, then we may need
* a ts_recent from the last segment.
*/
acknow = tp->t_flags & TF_ACKNOW;
/*
* First, discard tcpcb state, which includes stopping its timers and
* freeing it. tcp_discardcb() used to also release the inpcb, but
* that work is now done in the caller.
*
* Note: soisdisconnected() call used to be made in tcp_discardcb(),
* and might not be needed here any longer.
*/
tcp_discardcb(tp);
so = inp->inp_socket;
soisdisconnected(so);
tw->tw_cred = crhold(so->so_cred);
SOCK_LOCK(so);
tw->tw_so_options = so->so_options;
SOCK_UNLOCK(so);
if (acknow)
tcp_twrespond(tw, TH_ACK);
inp->inp_ppcb = tw;
inp->inp_flags |= INP_TIMEWAIT;
TCPSTATES_INC(TCPS_TIME_WAIT);
tcp_tw_2msl_reset(tw, 0);
/*
* If the inpcb owns the sole reference to the socket, then we can
* detach and free the socket as it is not needed in time wait.
*/
if (inp->inp_flags & INP_SOCKREF) {
KASSERT(so->so_state & SS_PROTOREF,
("tcp_twstart: !SS_PROTOREF"));
inp->inp_flags &= ~INP_SOCKREF;
INP_WUNLOCK(inp);
SOCK_LOCK(so);
so->so_state &= ~SS_PROTOREF;
sofree(so);
} else
INP_WUNLOCK(inp);
}
/*
* Returns 1 if the TIME_WAIT state was killed and we should start over,
* looking for a pcb in the listen state. Returns 0 otherwise.
*/
int
tcp_twcheck(struct inpcb *inp, struct tcpopt *to __unused, struct tcphdr *th,
struct mbuf *m, int tlen)
{
struct tcptw *tw;
int thflags;
tcp_seq seq;
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(inp);
/*
* XXXRW: Time wait state for inpcb has been recycled, but inpcb is
* still present. This is undesirable, but temporarily necessary
* until we work out how to handle inpcb's who's timewait state has
* been removed.
*/
tw = intotw(inp);
if (tw == NULL)
goto drop;
thflags = th->th_flags;
/*
* NOTE: for FIN_WAIT_2 (to be added later),
* must validate sequence number before accepting RST
*/
/*
* If the segment contains RST:
* Drop the segment - see Stevens, vol. 2, p. 964 and
* RFC 1337.
*/
if (thflags & TH_RST)
goto drop;
#if 0
/* PAWS not needed at the moment */
/*
* RFC 1323 PAWS: If we have a timestamp reply on this segment
* and it's less than ts_recent, drop it.
*/
if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
TSTMP_LT(to.to_tsval, tp->ts_recent)) {
if ((thflags & TH_ACK) == 0)
goto drop;
goto ack;
}
/*
* ts_recent is never updated because we never accept new segments.
*/
#endif
/*
* If a new connection request is received
* while in TIME_WAIT, drop the old connection
* and start over if the sequence numbers
* are above the previous ones.
*/
if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
tcp_twclose(tw, 0);
return (1);
}
/*
* Drop the segment if it does not contain an ACK.
*/
if ((thflags & TH_ACK) == 0)
goto drop;
/*
* Reset the 2MSL timer if this is a duplicate FIN.
*/
if (thflags & TH_FIN) {
seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
if (seq + 1 == tw->rcv_nxt)
tcp_tw_2msl_reset(tw, 1);
}
/*
* Acknowledge the segment if it has data or is not a duplicate ACK.
*/
if (thflags != TH_ACK || tlen != 0 ||
th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
tcp_twrespond(tw, TH_ACK);
drop:
INP_WUNLOCK(inp);
m_freem(m);
return (0);
}
void
tcp_twclose(struct tcptw *tw, int reuse)
{
struct socket *so;
struct inpcb *inp;
/*
* At this point, we are in one of two situations:
*
* (1) We have no socket, just an inpcb<->twtcp pair. We can free
* all state.
*
* (2) We have a socket -- if we own a reference, release it and
* notify the socket layer.
*/
inp = tw->tw_inpcb;
KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait"));
KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw"));
INP_INFO_RLOCK_ASSERT(&V_tcbinfo); /* in_pcbfree() */
INP_WLOCK_ASSERT(inp);
tcp_tw_2msl_stop(tw, reuse);
inp->inp_ppcb = NULL;
in_pcbdrop(inp);
so = inp->inp_socket;
if (so != NULL) {
/*
* If there's a socket, handle two cases: first, we own a
* strong reference, which we will now release, or we don't
* in which case another reference exists (XXXRW: think
* about this more), and we don't need to take action.
*/
if (inp->inp_flags & INP_SOCKREF) {
inp->inp_flags &= ~INP_SOCKREF;
INP_WUNLOCK(inp);
SOCK_LOCK(so);
KASSERT(so->so_state & SS_PROTOREF,
("tcp_twclose: INP_SOCKREF && !SS_PROTOREF"));
so->so_state &= ~SS_PROTOREF;
sofree(so);
} else {
/*
* If we don't own the only reference, the socket and
* inpcb need to be left around to be handled by
* tcp_usr_detach() later.
*/
INP_WUNLOCK(inp);
}
} else {
/*
* The socket has been already cleaned-up for us, only free the
* inpcb.
*/
in_pcbfree(inp);
}
TCPSTAT_INC(tcps_closed);
}
static int
tcp_twrespond(struct tcptw *tw, int flags)
{
struct inpcb *inp = tw->tw_inpcb;
#if defined(INET6) || defined(INET)
struct tcphdr *th = NULL;
#endif
struct mbuf *m;
#ifdef INET
struct ip *ip = NULL;
#endif
u_int hdrlen, optlen;
int error = 0; /* Keep compiler happy */
struct tcpopt to;
#ifdef INET6
struct ip6_hdr *ip6 = NULL;
int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
#endif
hdrlen = 0; /* Keep compiler happy */
INP_WLOCK_ASSERT(inp);
m = m_gethdr(M_NOWAIT, MT_DATA);
if (m == NULL)
return (ENOBUFS);
m->m_data += max_linkhdr;
#ifdef MAC
mac_inpcb_create_mbuf(inp, m);
#endif
#ifdef INET6
if (isipv6) {
hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
ip6 = mtod(m, struct ip6_hdr *);
th = (struct tcphdr *)(ip6 + 1);
tcpip_fillheaders(inp, ip6, th);
}
#endif
#if defined(INET6) && defined(INET)
else
#endif
#ifdef INET
{
hdrlen = sizeof(struct tcpiphdr);
ip = mtod(m, struct ip *);
th = (struct tcphdr *)(ip + 1);
tcpip_fillheaders(inp, ip, th);
}
#endif
to.to_flags = 0;
/*
* Send a timestamp and echo-reply if both our side and our peer
* have sent timestamps in our SYN's and this is not a RST.
*/
if (tw->t_recent && flags == TH_ACK) {
to.to_flags |= TOF_TS;
to.to_tsval = tcp_ts_getticks() + tw->ts_offset;
to.to_tsecr = tw->t_recent;
}
optlen = tcp_addoptions(&to, (u_char *)(th + 1));
m->m_len = hdrlen + optlen;
m->m_pkthdr.len = m->m_len;
KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
th->th_seq = htonl(tw->snd_nxt);
th->th_ack = htonl(tw->rcv_nxt);
th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
th->th_flags = flags;
th->th_win = htons(tw->last_win);
m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
#ifdef INET6
if (isipv6) {
m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
th->th_sum = in6_cksum_pseudo(ip6,
sizeof(struct tcphdr) + optlen, IPPROTO_TCP, 0);
ip6->ip6_hlim = in6_selecthlim(inp, NULL);
error = ip6_output(m, inp->in6p_outputopts, NULL,
(tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
}
#endif
#if defined(INET6) && defined(INET)
else
#endif
#ifdef INET
{
m->m_pkthdr.csum_flags = CSUM_TCP;
th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
ip->ip_len = htons(m->m_pkthdr.len);
if (V_path_mtu_discovery)
ip->ip_off |= htons(IP_DF);
error = ip_output(m, inp->inp_options, NULL,
((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
NULL, inp);
}
#endif
if (flags & TH_ACK)
TCPSTAT_INC(tcps_sndacks);
else
TCPSTAT_INC(tcps_sndctrl);
TCPSTAT_INC(tcps_sndtotal);
return (error);
}
static void
tcp_tw_2msl_reset(struct tcptw *tw, int rearm)
{
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(tw->tw_inpcb);
TW_WLOCK(V_tw_lock);
if (rearm)
TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
tw->tw_time = ticks + 2 * tcp_msl;
TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl);
TW_WUNLOCK(V_tw_lock);
}
static void
tcp_tw_2msl_stop(struct tcptw *tw, int reuse)
{
struct ucred *cred;
struct inpcb *inp;
int released;
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
TW_WLOCK(V_tw_lock);
inp = tw->tw_inpcb;
tw->tw_inpcb = NULL;
TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
cred = tw->tw_cred;
tw->tw_cred = NULL;
TW_WUNLOCK(V_tw_lock);
if (cred != NULL)
crfree(cred);
released = in_pcbrele_wlocked(inp);
KASSERT(!released, ("%s: inp should not be released here", __func__));
if (!reuse)
uma_zfree(V_tcptw_zone, tw);
TCPSTATES_DEC(TCPS_TIME_WAIT);
}
struct tcptw *
tcp_tw_2msl_scan(int reuse)
{
struct tcptw *tw;
struct inpcb *inp;
#ifdef INVARIANTS
if (reuse) {
/*
* Exclusive pcbinfo lock is not required in reuse case even if
* two inpcb locks can be acquired simultaneously:
* - the inpcb transitioning to TIME_WAIT state in
* tcp_tw_start(),
* - the inpcb closed by tcp_twclose().
*
* It is because only inpcbs in FIN_WAIT2 or CLOSING states can
* transition in TIME_WAIT state. Then a pcbcb cannot be in
* TIME_WAIT list and transitioning to TIME_WAIT state at same
* time.
*/
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
}
#endif
for (;;) {
TW_RLOCK(V_tw_lock);
tw = TAILQ_FIRST(&V_twq_2msl);
if (tw == NULL || (!reuse && (tw->tw_time - ticks) > 0)) {
TW_RUNLOCK(V_tw_lock);
break;
}
KASSERT(tw->tw_inpcb != NULL, ("%s: tw->tw_inpcb == NULL",
__func__));
inp = tw->tw_inpcb;
in_pcbref(inp);
TW_RUNLOCK(V_tw_lock);
if (INP_INFO_TRY_RLOCK(&V_tcbinfo)) {
INP_WLOCK(inp);
tw = intotw(inp);
if (in_pcbrele_wlocked(inp)) {
KASSERT(tw == NULL, ("%s: held last inp "
"reference but tw not NULL", __func__));
INP_INFO_RUNLOCK(&V_tcbinfo);
continue;
}
if (tw == NULL) {
/* tcp_twclose() has already been called */
INP_WUNLOCK(inp);
INP_INFO_RUNLOCK(&V_tcbinfo);
continue;
}
tcp_twclose(tw, reuse);
INP_INFO_RUNLOCK(&V_tcbinfo);
if (reuse)
return tw;
} else {
/* INP_INFO lock is busy, continue later. */
INP_WLOCK(inp);
if (!in_pcbrele_wlocked(inp))
INP_WUNLOCK(inp);
break;
}
}
return NULL;
}
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