Source to netinet/tcp_subr.c
/*
* Copyright (c) 1982, 1986, 1988, 1990 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. 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 7.20 (Berkeley) 12/1/90
*/
#include "param.h"
#include "systm.h"
#include "malloc.h"
#include "mbuf.h"
#include "socket.h"
#include "socketvar.h"
#include "protosw.h"
#include "errno.h"
#include "../net/route.h"
#include "../net/if.h"
#include "in.h"
#include "in_systm.h"
#include "ip.h"
#include "in_pcb.h"
#include "ip_var.h"
#include "ip_icmp.h"
#include "tcp.h"
#include "tcp_fsm.h"
#include "tcp_seq.h"
#include "tcp_timer.h"
#include "tcp_var.h"
#include "tcpip.h"
/* patchable/settable parameters for tcp */
int tcp_ttl = TCP_TTL;
int tcp_mssdflt = TCP_MSS;
int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;
extern struct inpcb *tcp_last_inpcb;
/*
* Tcp initialization
*/
tcp_init()
{
tcp_iss = 1; /* wrong */
tcb.inp_next = tcb.inp_prev = &tcb;
if (max_protohdr < sizeof(struct tcpiphdr))
max_protohdr = sizeof(struct tcpiphdr);
if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN)
panic("tcp_init");
}
/*
* Create template to be used to send tcp packets on a connection.
* Call after host entry created, allocates an mbuf and fills
* in a skeletal tcp/ip header, minimizing the amount of work
* necessary when the connection is used.
*/
struct tcpiphdr *
tcp_template(tp)
struct tcpcb *tp;
{
register struct inpcb *inp = tp->t_inpcb;
register struct mbuf *m;
register struct tcpiphdr *n;
if ((n = tp->t_template) == 0) {
m = m_get(M_DONTWAIT, MT_HEADER);
if (m == NULL)
return (0);
m->m_len = sizeof (struct tcpiphdr);
n = mtod(m, struct tcpiphdr *);
}
n->ti_next = n->ti_prev = 0;
n->ti_x1 = 0;
n->ti_pr = IPPROTO_TCP;
n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip));
n->ti_src = inp->inp_laddr;
n->ti_dst = inp->inp_faddr;
n->ti_sport = inp->inp_lport;
n->ti_dport = inp->inp_fport;
n->ti_seq = 0;
n->ti_ack = 0;
n->ti_x2 = 0;
n->ti_off = 5;
n->ti_flags = 0;
n->ti_win = 0;
n->ti_sum = 0;
n->ti_urp = 0;
return (n);
}
/*
* Send a single message to the TCP at address specified by
* the given TCP/IP header. If m == 0, then we make a copy
* of the tcpiphdr at ti and send directly to the addressed host.
* This is used to force keep alive messages out using the TCP
* template for a connection tp->t_template. If flags are given
* then we send a message back to the TCP which originated the
* segment ti, and discard the mbuf containing it and any other
* attached mbufs.
*
* In any case the ack and sequence number of the transmitted
* segment are as specified by the parameters.
*/
tcp_respond(tp, ti, m, ack, seq, flags)
struct tcpcb *tp;
register struct tcpiphdr *ti;
register struct mbuf *m;
tcp_seq ack, seq;
int flags;
{
register int tlen;
int win = 0;
struct route *ro = 0;
if (tp) {
win = sbspace(&tp->t_inpcb->inp_socket->so_rcv);
ro = &tp->t_inpcb->inp_route;
}
if (m == 0) {
m = m_gethdr(M_DONTWAIT, MT_HEADER);
if (m == NULL)
return;
#ifdef TCP_COMPAT_42
tlen = 1;
#else
tlen = 0;
#endif
m->m_data += max_linkhdr;
*mtod(m, struct tcpiphdr *) = *ti;
ti = mtod(m, struct tcpiphdr *);
flags = TH_ACK;
} else {
m_freem(m->m_next);
m->m_next = 0;
m->m_data = (caddr_t)ti;
m->m_len = sizeof (struct tcpiphdr);
tlen = 0;
#define xchg(a,b,type) { type t; t=a; a=b; b=t; }
xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long);
xchg(ti->ti_dport, ti->ti_sport, u_short);
#undef xchg
}
ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen));
tlen += sizeof (struct tcpiphdr);
m->m_len = tlen;
m->m_pkthdr.len = tlen;
m->m_pkthdr.rcvif = (struct ifnet *) 0;
ti->ti_next = ti->ti_prev = 0;
ti->ti_x1 = 0;
ti->ti_seq = htonl(seq);
ti->ti_ack = htonl(ack);
ti->ti_x2 = 0;
ti->ti_off = sizeof (struct tcphdr) >> 2;
ti->ti_flags = flags;
ti->ti_win = htons((u_short)win);
ti->ti_urp = 0;
ti->ti_sum = in_cksum(m, tlen);
((struct ip *)ti)->ip_len = tlen;
((struct ip *)ti)->ip_ttl = tcp_ttl;
(void) ip_output(m, (struct mbuf *)0, ro, 0);
}
/*
* Create a new TCP control block, making an
* empty reassembly queue and hooking it to the argument
* protocol control block.
*/
struct tcpcb *
tcp_newtcpcb(inp)
struct inpcb *inp;
{
struct mbuf *m = m_getclr(M_DONTWAIT, MT_PCB);
register struct tcpcb *tp;
if (m == NULL)
return ((struct tcpcb *)0);
tp = mtod(m, struct tcpcb *);
tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp;
tp->t_maxseg = tcp_mssdflt;
tp->t_flags = 0; /* sends options! */
tp->t_inpcb = inp;
/*
* Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
* rtt estimate. Set rttvar so that srtt + 2 * rttvar gives
* reasonable initial retransmit time.
*/
tp->t_srtt = TCPTV_SRTTBASE;
tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << 2;
tp->t_rttmin = TCPTV_MIN;
TCPT_RANGESET(tp->t_rxtcur,
((TCPTV_SRTTBASE >> 2) + (TCPTV_SRTTDFLT << 2)) >> 1,
TCPTV_MIN, TCPTV_REXMTMAX);
tp->snd_cwnd = TCP_MAXWIN;
tp->snd_ssthresh = TCP_MAXWIN;
inp->inp_ip.ip_ttl = tcp_ttl;
inp->inp_ppcb = (caddr_t)tp;
return (tp);
}
/*
* Drop a TCP connection, reporting
* the specified error. If connection is synchronized,
* then send a RST to peer.
*/
struct tcpcb *
tcp_drop(tp, errno)
register struct tcpcb *tp;
int errno;
{
struct socket *so = tp->t_inpcb->inp_socket;
if (TCPS_HAVERCVDSYN(tp->t_state)) {
tp->t_state = TCPS_CLOSED;
(void) tcp_output(tp);
tcpstat.tcps_drops++;
} else
tcpstat.tcps_conndrops++;
if (errno == ETIMEDOUT && tp->t_softerror)
errno = tp->t_softerror;
so->so_error = errno;
return (tcp_close(tp));
}
/*
* Close a TCP control block:
* discard all space held by the tcp
* discard internet protocol block
* wake up any sleepers
*/
struct tcpcb *
tcp_close(tp)
register struct tcpcb *tp;
{
register struct tcpiphdr *t;
struct inpcb *inp = tp->t_inpcb;
struct socket *so = inp->inp_socket;
register struct mbuf *m;
#ifdef RTV_RTT
register struct rtentry *rt;
/*
* If we sent enough data to get some meaningful characteristics,
* save them in the routing entry. 'Enough' is arbitrarily
* defined as the sendpipesize (default 4K) * 16. This would
* give us 16 rtt samples assuming we only get one sample per
* window (the usual case on a long haul net). 16 samples is
* enough for the srtt filter to converge to within 5% of the correct
* value; fewer samples and we could save a very bogus rtt.
*
* Don't update the default route's characteristics and don't
* update anything that the user "locked".
*/
if (SEQ_LT(tp->iss + so->so_snd.sb_hiwat * 16, tp->snd_max) &&
(rt = inp->inp_route.ro_rt) &&
((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr != INADDR_ANY) {
register u_long i;
if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) {
i = tp->t_srtt *
(RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE));
if (rt->rt_rmx.rmx_rtt && i)
/*
* filter this update to half the old & half
* the new values, converting scale.
* See route.h and tcp_var.h for a
* description of the scaling constants.
*/
rt->rt_rmx.rmx_rtt =
(rt->rt_rmx.rmx_rtt + i) / 2;
else
rt->rt_rmx.rmx_rtt = i;
}
if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) {
i = tp->t_rttvar *
(RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE));
if (rt->rt_rmx.rmx_rttvar && i)
rt->rt_rmx.rmx_rttvar =
(rt->rt_rmx.rmx_rttvar + i) / 2;
else
rt->rt_rmx.rmx_rttvar = i;
}
/*
* update the pipelimit (ssthresh) if it has been updated
* already or if a pipesize was specified & the threshhold
* got below half the pipesize. I.e., wait for bad news
* before we start updating, then update on both good
* and bad news.
*/
if ((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 &&
(i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh ||
i < (rt->rt_rmx.rmx_sendpipe / 2)) {
/*
* convert the limit from user data bytes to
* packets then to packet data bytes.
*/
i = (i + tp->t_maxseg / 2) / tp->t_maxseg;
if (i < 2)
i = 2;
i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr));
if (rt->rt_rmx.rmx_ssthresh)
rt->rt_rmx.rmx_ssthresh =
(rt->rt_rmx.rmx_ssthresh + i) / 2;
else
rt->rt_rmx.rmx_ssthresh = i;
}
}
#endif RTV_RTT
/* free the reassembly queue, if any */
t = tp->seg_next;
while (t != (struct tcpiphdr *)tp) {
t = (struct tcpiphdr *)t->ti_next;
m = REASS_MBUF((struct tcpiphdr *)t->ti_prev);
remque(t->ti_prev);
m_freem(m);
}
if (tp->t_template)
(void) m_free(dtom(tp->t_template));
(void) m_free(dtom(tp));
inp->inp_ppcb = 0;
soisdisconnected(so);
/* clobber input pcb cache if we're closing the cached connection */
if (inp == tcp_last_inpcb)
tcp_last_inpcb = &tcb;
in_pcbdetach(inp);
tcpstat.tcps_closed++;
return ((struct tcpcb *)0);
}
tcp_drain()
{
}
/*
* Notify a tcp user of an asynchronous error;
* store error as soft error, but wake up user
* (for now, won't do anything until can select for soft error).
*/
tcp_notify(inp, error)
register struct inpcb *inp;
int error;
{
((struct tcpcb *)inp->inp_ppcb)->t_softerror = error;
wakeup((caddr_t) &inp->inp_socket->so_timeo);
sorwakeup(inp->inp_socket);
sowwakeup(inp->inp_socket);
}
tcp_ctlinput(cmd, sa, ip)
int cmd;
struct sockaddr *sa;
register struct ip *ip;
{
register struct tcphdr *th;
extern struct in_addr zeroin_addr;
extern u_char inetctlerrmap[];
int (*notify)() = tcp_notify, tcp_quench();
if (cmd == PRC_QUENCH)
notify = tcp_quench;
else if ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0)
return;
if (ip) {
th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2));
in_pcbnotify(&tcb, sa, th->th_dport, ip->ip_src, th->th_sport,
cmd, notify);
} else
in_pcbnotify(&tcb, sa, 0, zeroin_addr, 0, cmd, notify);
}
/*
* When a source quench is received, close congestion window
* to one segment. We will gradually open it again as we proceed.
*/
tcp_quench(inp)
struct inpcb *inp;
{
struct tcpcb *tp = intotcpcb(inp);
if (tp)
tp->snd_cwnd = tp->t_maxseg;
}