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62 |
marcus.erl |
/*
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| 2 |
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* INET An implementation of the TCP/IP protocol suite for the LINUX
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| 3 |
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* operating system. INET is implemented using the BSD Socket
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| 4 |
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* interface as the means of communication with the user level.
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*
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* Implementation of the Transmission Control Protocol(TCP).
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*
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* Version: $Id: tcp_minisocks.c,v 1.15 2002/02/01 22:01:04 davem Exp $
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*
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* Authors: Ross Biro
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* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
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* Mark Evans, <evansmp@uhura.aston.ac.uk>
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* Corey Minyard <wf-rch!minyard@relay.EU.net>
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| 14 |
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* Florian La Roche, <flla@stud.uni-sb.de>
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* Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
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* Linus Torvalds, <torvalds@cs.helsinki.fi>
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* Alan Cox, <gw4pts@gw4pts.ampr.org>
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* Matthew Dillon, <dillon@apollo.west.oic.com>
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* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
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* Jorge Cwik, <jorge@laser.satlink.net>
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*/
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| 23 |
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#include <linux/mm.h>
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| 24 |
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#include <linux/module.h>
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| 25 |
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#include <linux/sysctl.h>
|
| 26 |
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#include <linux/workqueue.h>
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| 27 |
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#include <net/tcp.h>
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| 28 |
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#include <net/inet_common.h>
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| 29 |
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#include <net/xfrm.h>
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| 30 |
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| 31 |
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#ifdef CONFIG_SYSCTL
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| 32 |
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#define SYNC_INIT 0 /* let the user enable it */
|
| 33 |
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#else
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| 34 |
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#define SYNC_INIT 1
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| 35 |
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#endif
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| 36 |
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| 37 |
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int sysctl_tcp_syncookies __read_mostly = SYNC_INIT;
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| 38 |
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int sysctl_tcp_abort_on_overflow __read_mostly;
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| 39 |
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| 40 |
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struct inet_timewait_death_row tcp_death_row = {
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| 41 |
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.sysctl_max_tw_buckets = NR_FILE * 2,
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| 42 |
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.period = TCP_TIMEWAIT_LEN / INET_TWDR_TWKILL_SLOTS,
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| 43 |
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.death_lock = __SPIN_LOCK_UNLOCKED(tcp_death_row.death_lock),
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| 44 |
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.hashinfo = &tcp_hashinfo,
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| 45 |
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.tw_timer = TIMER_INITIALIZER(inet_twdr_hangman, 0,
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| 46 |
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(unsigned long)&tcp_death_row),
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| 47 |
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.twkill_work = __WORK_INITIALIZER(tcp_death_row.twkill_work,
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| 48 |
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inet_twdr_twkill_work),
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| 49 |
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/* Short-time timewait calendar */
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| 50 |
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| 51 |
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.twcal_hand = -1,
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| 52 |
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.twcal_timer = TIMER_INITIALIZER(inet_twdr_twcal_tick, 0,
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| 53 |
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(unsigned long)&tcp_death_row),
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| 54 |
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};
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| 55 |
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| 56 |
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EXPORT_SYMBOL_GPL(tcp_death_row);
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| 57 |
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| 58 |
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static __inline__ int tcp_in_window(u32 seq, u32 end_seq, u32 s_win, u32 e_win)
|
| 59 |
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{
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| 60 |
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if (seq == s_win)
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| 61 |
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return 1;
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| 62 |
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if (after(end_seq, s_win) && before(seq, e_win))
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| 63 |
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return 1;
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| 64 |
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return (seq == e_win && seq == end_seq);
|
| 65 |
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}
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| 66 |
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|
| 67 |
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/*
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| 68 |
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* * Main purpose of TIME-WAIT state is to close connection gracefully,
|
| 69 |
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* when one of ends sits in LAST-ACK or CLOSING retransmitting FIN
|
| 70 |
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* (and, probably, tail of data) and one or more our ACKs are lost.
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| 71 |
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* * What is TIME-WAIT timeout? It is associated with maximal packet
|
| 72 |
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* lifetime in the internet, which results in wrong conclusion, that
|
| 73 |
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* it is set to catch "old duplicate segments" wandering out of their path.
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| 74 |
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* It is not quite correct. This timeout is calculated so that it exceeds
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| 75 |
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* maximal retransmission timeout enough to allow to lose one (or more)
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| 76 |
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* segments sent by peer and our ACKs. This time may be calculated from RTO.
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| 77 |
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* * When TIME-WAIT socket receives RST, it means that another end
|
| 78 |
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* finally closed and we are allowed to kill TIME-WAIT too.
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| 79 |
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* * Second purpose of TIME-WAIT is catching old duplicate segments.
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| 80 |
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* Well, certainly it is pure paranoia, but if we load TIME-WAIT
|
| 81 |
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* with this semantics, we MUST NOT kill TIME-WAIT state with RSTs.
|
| 82 |
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* * If we invented some more clever way to catch duplicates
|
| 83 |
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* (f.e. based on PAWS), we could truncate TIME-WAIT to several RTOs.
|
| 84 |
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*
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| 85 |
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* The algorithm below is based on FORMAL INTERPRETATION of RFCs.
|
| 86 |
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* When you compare it to RFCs, please, read section SEGMENT ARRIVES
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| 87 |
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* from the very beginning.
|
| 88 |
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*
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| 89 |
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* NOTE. With recycling (and later with fin-wait-2) TW bucket
|
| 90 |
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* is _not_ stateless. It means, that strictly speaking we must
|
| 91 |
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* spinlock it. I do not want! Well, probability of misbehaviour
|
| 92 |
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* is ridiculously low and, seems, we could use some mb() tricks
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| 93 |
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* to avoid misread sequence numbers, states etc. --ANK
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| 94 |
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*/
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| 95 |
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enum tcp_tw_status
|
| 96 |
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tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
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| 97 |
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const struct tcphdr *th)
|
| 98 |
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{
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| 99 |
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struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
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struct tcp_options_received tmp_opt;
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| 101 |
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int paws_reject = 0;
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| 102 |
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| 103 |
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tmp_opt.saw_tstamp = 0;
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| 104 |
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if (th->doff > (sizeof(*th) >> 2) && tcptw->tw_ts_recent_stamp) {
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| 105 |
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tcp_parse_options(skb, &tmp_opt, 0);
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| 107 |
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if (tmp_opt.saw_tstamp) {
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| 108 |
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tmp_opt.ts_recent = tcptw->tw_ts_recent;
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| 109 |
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tmp_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
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| 110 |
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paws_reject = tcp_paws_check(&tmp_opt, th->rst);
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| 111 |
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}
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| 112 |
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}
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| 113 |
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|
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| 114 |
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if (tw->tw_substate == TCP_FIN_WAIT2) {
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| 115 |
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/* Just repeat all the checks of tcp_rcv_state_process() */
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| 116 |
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| 117 |
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/* Out of window, send ACK */
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| 118 |
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if (paws_reject ||
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| 119 |
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!tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
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| 120 |
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tcptw->tw_rcv_nxt,
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| 121 |
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tcptw->tw_rcv_nxt + tcptw->tw_rcv_wnd))
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| 122 |
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return TCP_TW_ACK;
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| 123 |
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|
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| 124 |
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if (th->rst)
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| 125 |
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goto kill;
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| 126 |
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| 127 |
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if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt))
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| 128 |
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goto kill_with_rst;
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| 129 |
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| 130 |
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/* Dup ACK? */
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| 131 |
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if (!after(TCP_SKB_CB(skb)->end_seq, tcptw->tw_rcv_nxt) ||
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TCP_SKB_CB(skb)->end_seq == TCP_SKB_CB(skb)->seq) {
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| 133 |
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inet_twsk_put(tw);
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| 134 |
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return TCP_TW_SUCCESS;
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| 135 |
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}
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| 136 |
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| 137 |
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/* New data or FIN. If new data arrive after half-duplex close,
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| 138 |
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* reset.
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| 139 |
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*/
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| 140 |
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if (!th->fin ||
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| 141 |
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TCP_SKB_CB(skb)->end_seq != tcptw->tw_rcv_nxt + 1) {
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| 142 |
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kill_with_rst:
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inet_twsk_deschedule(tw, &tcp_death_row);
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| 144 |
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inet_twsk_put(tw);
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| 145 |
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return TCP_TW_RST;
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| 146 |
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}
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| 147 |
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| 148 |
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/* FIN arrived, enter true time-wait state. */
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| 149 |
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tw->tw_substate = TCP_TIME_WAIT;
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| 150 |
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tcptw->tw_rcv_nxt = TCP_SKB_CB(skb)->end_seq;
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| 151 |
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if (tmp_opt.saw_tstamp) {
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| 152 |
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tcptw->tw_ts_recent_stamp = get_seconds();
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| 153 |
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tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
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| 154 |
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}
|
| 155 |
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|
| 156 |
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/* I am shamed, but failed to make it more elegant.
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| 157 |
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* Yes, it is direct reference to IP, which is impossible
|
| 158 |
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* to generalize to IPv6. Taking into account that IPv6
|
| 159 |
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* do not understand recycling in any case, it not
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| 160 |
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* a big problem in practice. --ANK */
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| 161 |
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if (tw->tw_family == AF_INET &&
|
| 162 |
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tcp_death_row.sysctl_tw_recycle && tcptw->tw_ts_recent_stamp &&
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| 163 |
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tcp_v4_tw_remember_stamp(tw))
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| 164 |
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inet_twsk_schedule(tw, &tcp_death_row, tw->tw_timeout,
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| 165 |
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TCP_TIMEWAIT_LEN);
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| 166 |
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else
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| 167 |
|
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inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
|
| 168 |
|
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TCP_TIMEWAIT_LEN);
|
| 169 |
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return TCP_TW_ACK;
|
| 170 |
|
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}
|
| 171 |
|
|
|
| 172 |
|
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/*
|
| 173 |
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* Now real TIME-WAIT state.
|
| 174 |
|
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*
|
| 175 |
|
|
* RFC 1122:
|
| 176 |
|
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* "When a connection is [...] on TIME-WAIT state [...]
|
| 177 |
|
|
* [a TCP] MAY accept a new SYN from the remote TCP to
|
| 178 |
|
|
* reopen the connection directly, if it:
|
| 179 |
|
|
*
|
| 180 |
|
|
* (1) assigns its initial sequence number for the new
|
| 181 |
|
|
* connection to be larger than the largest sequence
|
| 182 |
|
|
* number it used on the previous connection incarnation,
|
| 183 |
|
|
* and
|
| 184 |
|
|
*
|
| 185 |
|
|
* (2) returns to TIME-WAIT state if the SYN turns out
|
| 186 |
|
|
* to be an old duplicate".
|
| 187 |
|
|
*/
|
| 188 |
|
|
|
| 189 |
|
|
if (!paws_reject &&
|
| 190 |
|
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(TCP_SKB_CB(skb)->seq == tcptw->tw_rcv_nxt &&
|
| 191 |
|
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(TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq || th->rst))) {
|
| 192 |
|
|
/* In window segment, it may be only reset or bare ack. */
|
| 193 |
|
|
|
| 194 |
|
|
if (th->rst) {
|
| 195 |
|
|
/* This is TIME_WAIT assassination, in two flavors.
|
| 196 |
|
|
* Oh well... nobody has a sufficient solution to this
|
| 197 |
|
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* protocol bug yet.
|
| 198 |
|
|
*/
|
| 199 |
|
|
if (sysctl_tcp_rfc1337 == 0) {
|
| 200 |
|
|
kill:
|
| 201 |
|
|
inet_twsk_deschedule(tw, &tcp_death_row);
|
| 202 |
|
|
inet_twsk_put(tw);
|
| 203 |
|
|
return TCP_TW_SUCCESS;
|
| 204 |
|
|
}
|
| 205 |
|
|
}
|
| 206 |
|
|
inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
|
| 207 |
|
|
TCP_TIMEWAIT_LEN);
|
| 208 |
|
|
|
| 209 |
|
|
if (tmp_opt.saw_tstamp) {
|
| 210 |
|
|
tcptw->tw_ts_recent = tmp_opt.rcv_tsval;
|
| 211 |
|
|
tcptw->tw_ts_recent_stamp = get_seconds();
|
| 212 |
|
|
}
|
| 213 |
|
|
|
| 214 |
|
|
inet_twsk_put(tw);
|
| 215 |
|
|
return TCP_TW_SUCCESS;
|
| 216 |
|
|
}
|
| 217 |
|
|
|
| 218 |
|
|
/* Out of window segment.
|
| 219 |
|
|
|
| 220 |
|
|
All the segments are ACKed immediately.
|
| 221 |
|
|
|
| 222 |
|
|
The only exception is new SYN. We accept it, if it is
|
| 223 |
|
|
not old duplicate and we are not in danger to be killed
|
| 224 |
|
|
by delayed old duplicates. RFC check is that it has
|
| 225 |
|
|
newer sequence number works at rates <40Mbit/sec.
|
| 226 |
|
|
However, if paws works, it is reliable AND even more,
|
| 227 |
|
|
we even may relax silly seq space cutoff.
|
| 228 |
|
|
|
| 229 |
|
|
RED-PEN: we violate main RFC requirement, if this SYN will appear
|
| 230 |
|
|
old duplicate (i.e. we receive RST in reply to SYN-ACK),
|
| 231 |
|
|
we must return socket to time-wait state. It is not good,
|
| 232 |
|
|
but not fatal yet.
|
| 233 |
|
|
*/
|
| 234 |
|
|
|
| 235 |
|
|
if (th->syn && !th->rst && !th->ack && !paws_reject &&
|
| 236 |
|
|
(after(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt) ||
|
| 237 |
|
|
(tmp_opt.saw_tstamp &&
|
| 238 |
|
|
(s32)(tcptw->tw_ts_recent - tmp_opt.rcv_tsval) < 0))) {
|
| 239 |
|
|
u32 isn = tcptw->tw_snd_nxt + 65535 + 2;
|
| 240 |
|
|
if (isn == 0)
|
| 241 |
|
|
isn++;
|
| 242 |
|
|
TCP_SKB_CB(skb)->when = isn;
|
| 243 |
|
|
return TCP_TW_SYN;
|
| 244 |
|
|
}
|
| 245 |
|
|
|
| 246 |
|
|
if (paws_reject)
|
| 247 |
|
|
NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
|
| 248 |
|
|
|
| 249 |
|
|
if (!th->rst) {
|
| 250 |
|
|
/* In this case we must reset the TIMEWAIT timer.
|
| 251 |
|
|
*
|
| 252 |
|
|
* If it is ACKless SYN it may be both old duplicate
|
| 253 |
|
|
* and new good SYN with random sequence number <rcv_nxt.
|
| 254 |
|
|
* Do not reschedule in the last case.
|
| 255 |
|
|
*/
|
| 256 |
|
|
if (paws_reject || th->ack)
|
| 257 |
|
|
inet_twsk_schedule(tw, &tcp_death_row, TCP_TIMEWAIT_LEN,
|
| 258 |
|
|
TCP_TIMEWAIT_LEN);
|
| 259 |
|
|
|
| 260 |
|
|
/* Send ACK. Note, we do not put the bucket,
|
| 261 |
|
|
* it will be released by caller.
|
| 262 |
|
|
*/
|
| 263 |
|
|
return TCP_TW_ACK;
|
| 264 |
|
|
}
|
| 265 |
|
|
inet_twsk_put(tw);
|
| 266 |
|
|
return TCP_TW_SUCCESS;
|
| 267 |
|
|
}
|
| 268 |
|
|
|
| 269 |
|
|
/*
|
| 270 |
|
|
* Move a socket to time-wait or dead fin-wait-2 state.
|
| 271 |
|
|
*/
|
| 272 |
|
|
void tcp_time_wait(struct sock *sk, int state, int timeo)
|
| 273 |
|
|
{
|
| 274 |
|
|
struct inet_timewait_sock *tw = NULL;
|
| 275 |
|
|
const struct inet_connection_sock *icsk = inet_csk(sk);
|
| 276 |
|
|
const struct tcp_sock *tp = tcp_sk(sk);
|
| 277 |
|
|
int recycle_ok = 0;
|
| 278 |
|
|
|
| 279 |
|
|
if (tcp_death_row.sysctl_tw_recycle && tp->rx_opt.ts_recent_stamp)
|
| 280 |
|
|
recycle_ok = icsk->icsk_af_ops->remember_stamp(sk);
|
| 281 |
|
|
|
| 282 |
|
|
if (tcp_death_row.tw_count < tcp_death_row.sysctl_max_tw_buckets)
|
| 283 |
|
|
tw = inet_twsk_alloc(sk, state);
|
| 284 |
|
|
|
| 285 |
|
|
if (tw != NULL) {
|
| 286 |
|
|
struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
|
| 287 |
|
|
const int rto = (icsk->icsk_rto << 2) - (icsk->icsk_rto >> 1);
|
| 288 |
|
|
|
| 289 |
|
|
tw->tw_rcv_wscale = tp->rx_opt.rcv_wscale;
|
| 290 |
|
|
tcptw->tw_rcv_nxt = tp->rcv_nxt;
|
| 291 |
|
|
tcptw->tw_snd_nxt = tp->snd_nxt;
|
| 292 |
|
|
tcptw->tw_rcv_wnd = tcp_receive_window(tp);
|
| 293 |
|
|
tcptw->tw_ts_recent = tp->rx_opt.ts_recent;
|
| 294 |
|
|
tcptw->tw_ts_recent_stamp = tp->rx_opt.ts_recent_stamp;
|
| 295 |
|
|
|
| 296 |
|
|
#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
|
| 297 |
|
|
if (tw->tw_family == PF_INET6) {
|
| 298 |
|
|
struct ipv6_pinfo *np = inet6_sk(sk);
|
| 299 |
|
|
struct inet6_timewait_sock *tw6;
|
| 300 |
|
|
|
| 301 |
|
|
tw->tw_ipv6_offset = inet6_tw_offset(sk->sk_prot);
|
| 302 |
|
|
tw6 = inet6_twsk((struct sock *)tw);
|
| 303 |
|
|
ipv6_addr_copy(&tw6->tw_v6_daddr, &np->daddr);
|
| 304 |
|
|
ipv6_addr_copy(&tw6->tw_v6_rcv_saddr, &np->rcv_saddr);
|
| 305 |
|
|
tw->tw_ipv6only = np->ipv6only;
|
| 306 |
|
|
}
|
| 307 |
|
|
#endif
|
| 308 |
|
|
|
| 309 |
|
|
#ifdef CONFIG_TCP_MD5SIG
|
| 310 |
|
|
/*
|
| 311 |
|
|
* The timewait bucket does not have the key DB from the
|
| 312 |
|
|
* sock structure. We just make a quick copy of the
|
| 313 |
|
|
* md5 key being used (if indeed we are using one)
|
| 314 |
|
|
* so the timewait ack generating code has the key.
|
| 315 |
|
|
*/
|
| 316 |
|
|
do {
|
| 317 |
|
|
struct tcp_md5sig_key *key;
|
| 318 |
|
|
memset(tcptw->tw_md5_key, 0, sizeof(tcptw->tw_md5_key));
|
| 319 |
|
|
tcptw->tw_md5_keylen = 0;
|
| 320 |
|
|
key = tp->af_specific->md5_lookup(sk, sk);
|
| 321 |
|
|
if (key != NULL) {
|
| 322 |
|
|
memcpy(&tcptw->tw_md5_key, key->key, key->keylen);
|
| 323 |
|
|
tcptw->tw_md5_keylen = key->keylen;
|
| 324 |
|
|
if (tcp_alloc_md5sig_pool() == NULL)
|
| 325 |
|
|
BUG();
|
| 326 |
|
|
}
|
| 327 |
|
|
} while (0);
|
| 328 |
|
|
#endif
|
| 329 |
|
|
|
| 330 |
|
|
/* Linkage updates. */
|
| 331 |
|
|
__inet_twsk_hashdance(tw, sk, &tcp_hashinfo);
|
| 332 |
|
|
|
| 333 |
|
|
/* Get the TIME_WAIT timeout firing. */
|
| 334 |
|
|
if (timeo < rto)
|
| 335 |
|
|
timeo = rto;
|
| 336 |
|
|
|
| 337 |
|
|
if (recycle_ok) {
|
| 338 |
|
|
tw->tw_timeout = rto;
|
| 339 |
|
|
} else {
|
| 340 |
|
|
tw->tw_timeout = TCP_TIMEWAIT_LEN;
|
| 341 |
|
|
if (state == TCP_TIME_WAIT)
|
| 342 |
|
|
timeo = TCP_TIMEWAIT_LEN;
|
| 343 |
|
|
}
|
| 344 |
|
|
|
| 345 |
|
|
inet_twsk_schedule(tw, &tcp_death_row, timeo,
|
| 346 |
|
|
TCP_TIMEWAIT_LEN);
|
| 347 |
|
|
inet_twsk_put(tw);
|
| 348 |
|
|
} else {
|
| 349 |
|
|
/* Sorry, if we're out of memory, just CLOSE this
|
| 350 |
|
|
* socket up. We've got bigger problems than
|
| 351 |
|
|
* non-graceful socket closings.
|
| 352 |
|
|
*/
|
| 353 |
|
|
LIMIT_NETDEBUG(KERN_INFO "TCP: time wait bucket table overflow\n");
|
| 354 |
|
|
}
|
| 355 |
|
|
|
| 356 |
|
|
tcp_update_metrics(sk);
|
| 357 |
|
|
tcp_done(sk);
|
| 358 |
|
|
}
|
| 359 |
|
|
|
| 360 |
|
|
void tcp_twsk_destructor(struct sock *sk)
|
| 361 |
|
|
{
|
| 362 |
|
|
#ifdef CONFIG_TCP_MD5SIG
|
| 363 |
|
|
struct tcp_timewait_sock *twsk = tcp_twsk(sk);
|
| 364 |
|
|
if (twsk->tw_md5_keylen)
|
| 365 |
|
|
tcp_put_md5sig_pool();
|
| 366 |
|
|
#endif
|
| 367 |
|
|
}
|
| 368 |
|
|
|
| 369 |
|
|
EXPORT_SYMBOL_GPL(tcp_twsk_destructor);
|
| 370 |
|
|
|
| 371 |
|
|
static inline void TCP_ECN_openreq_child(struct tcp_sock *tp,
|
| 372 |
|
|
struct request_sock *req)
|
| 373 |
|
|
{
|
| 374 |
|
|
tp->ecn_flags = inet_rsk(req)->ecn_ok ? TCP_ECN_OK : 0;
|
| 375 |
|
|
}
|
| 376 |
|
|
|
| 377 |
|
|
/* This is not only more efficient than what we used to do, it eliminates
|
| 378 |
|
|
* a lot of code duplication between IPv4/IPv6 SYN recv processing. -DaveM
|
| 379 |
|
|
*
|
| 380 |
|
|
* Actually, we could lots of memory writes here. tp of listening
|
| 381 |
|
|
* socket contains all necessary default parameters.
|
| 382 |
|
|
*/
|
| 383 |
|
|
struct sock *tcp_create_openreq_child(struct sock *sk, struct request_sock *req, struct sk_buff *skb)
|
| 384 |
|
|
{
|
| 385 |
|
|
struct sock *newsk = inet_csk_clone(sk, req, GFP_ATOMIC);
|
| 386 |
|
|
|
| 387 |
|
|
if (newsk != NULL) {
|
| 388 |
|
|
const struct inet_request_sock *ireq = inet_rsk(req);
|
| 389 |
|
|
struct tcp_request_sock *treq = tcp_rsk(req);
|
| 390 |
|
|
struct inet_connection_sock *newicsk = inet_csk(newsk);
|
| 391 |
|
|
struct tcp_sock *newtp;
|
| 392 |
|
|
|
| 393 |
|
|
/* Now setup tcp_sock */
|
| 394 |
|
|
newtp = tcp_sk(newsk);
|
| 395 |
|
|
newtp->pred_flags = 0;
|
| 396 |
|
|
newtp->rcv_wup = newtp->copied_seq = newtp->rcv_nxt = treq->rcv_isn + 1;
|
| 397 |
|
|
newtp->snd_sml = newtp->snd_una = newtp->snd_nxt = treq->snt_isn + 1;
|
| 398 |
|
|
|
| 399 |
|
|
tcp_prequeue_init(newtp);
|
| 400 |
|
|
|
| 401 |
|
|
tcp_init_wl(newtp, treq->snt_isn, treq->rcv_isn);
|
| 402 |
|
|
|
| 403 |
|
|
newtp->srtt = 0;
|
| 404 |
|
|
newtp->mdev = TCP_TIMEOUT_INIT;
|
| 405 |
|
|
newicsk->icsk_rto = TCP_TIMEOUT_INIT;
|
| 406 |
|
|
|
| 407 |
|
|
newtp->packets_out = 0;
|
| 408 |
|
|
newtp->retrans_out = 0;
|
| 409 |
|
|
newtp->sacked_out = 0;
|
| 410 |
|
|
newtp->fackets_out = 0;
|
| 411 |
|
|
newtp->snd_ssthresh = 0x7fffffff;
|
| 412 |
|
|
|
| 413 |
|
|
/* So many TCP implementations out there (incorrectly) count the
|
| 414 |
|
|
* initial SYN frame in their delayed-ACK and congestion control
|
| 415 |
|
|
* algorithms that we must have the following bandaid to talk
|
| 416 |
|
|
* efficiently to them. -DaveM
|
| 417 |
|
|
*/
|
| 418 |
|
|
newtp->snd_cwnd = 2;
|
| 419 |
|
|
newtp->snd_cwnd_cnt = 0;
|
| 420 |
|
|
newtp->bytes_acked = 0;
|
| 421 |
|
|
|
| 422 |
|
|
newtp->frto_counter = 0;
|
| 423 |
|
|
newtp->frto_highmark = 0;
|
| 424 |
|
|
|
| 425 |
|
|
newicsk->icsk_ca_ops = &tcp_init_congestion_ops;
|
| 426 |
|
|
|
| 427 |
|
|
tcp_set_ca_state(newsk, TCP_CA_Open);
|
| 428 |
|
|
tcp_init_xmit_timers(newsk);
|
| 429 |
|
|
skb_queue_head_init(&newtp->out_of_order_queue);
|
| 430 |
|
|
newtp->write_seq = treq->snt_isn + 1;
|
| 431 |
|
|
newtp->pushed_seq = newtp->write_seq;
|
| 432 |
|
|
|
| 433 |
|
|
newtp->rx_opt.saw_tstamp = 0;
|
| 434 |
|
|
|
| 435 |
|
|
newtp->rx_opt.dsack = 0;
|
| 436 |
|
|
newtp->rx_opt.eff_sacks = 0;
|
| 437 |
|
|
|
| 438 |
|
|
newtp->rx_opt.num_sacks = 0;
|
| 439 |
|
|
newtp->urg_data = 0;
|
| 440 |
|
|
|
| 441 |
|
|
if (sock_flag(newsk, SOCK_KEEPOPEN))
|
| 442 |
|
|
inet_csk_reset_keepalive_timer(newsk,
|
| 443 |
|
|
keepalive_time_when(newtp));
|
| 444 |
|
|
|
| 445 |
|
|
newtp->rx_opt.tstamp_ok = ireq->tstamp_ok;
|
| 446 |
|
|
if ((newtp->rx_opt.sack_ok = ireq->sack_ok) != 0) {
|
| 447 |
|
|
if (sysctl_tcp_fack)
|
| 448 |
|
|
tcp_enable_fack(newtp);
|
| 449 |
|
|
}
|
| 450 |
|
|
newtp->window_clamp = req->window_clamp;
|
| 451 |
|
|
newtp->rcv_ssthresh = req->rcv_wnd;
|
| 452 |
|
|
newtp->rcv_wnd = req->rcv_wnd;
|
| 453 |
|
|
newtp->rx_opt.wscale_ok = ireq->wscale_ok;
|
| 454 |
|
|
if (newtp->rx_opt.wscale_ok) {
|
| 455 |
|
|
newtp->rx_opt.snd_wscale = ireq->snd_wscale;
|
| 456 |
|
|
newtp->rx_opt.rcv_wscale = ireq->rcv_wscale;
|
| 457 |
|
|
} else {
|
| 458 |
|
|
newtp->rx_opt.snd_wscale = newtp->rx_opt.rcv_wscale = 0;
|
| 459 |
|
|
newtp->window_clamp = min(newtp->window_clamp, 65535U);
|
| 460 |
|
|
}
|
| 461 |
|
|
newtp->snd_wnd = (ntohs(tcp_hdr(skb)->window) <<
|
| 462 |
|
|
newtp->rx_opt.snd_wscale);
|
| 463 |
|
|
newtp->max_window = newtp->snd_wnd;
|
| 464 |
|
|
|
| 465 |
|
|
if (newtp->rx_opt.tstamp_ok) {
|
| 466 |
|
|
newtp->rx_opt.ts_recent = req->ts_recent;
|
| 467 |
|
|
newtp->rx_opt.ts_recent_stamp = get_seconds();
|
| 468 |
|
|
newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
|
| 469 |
|
|
} else {
|
| 470 |
|
|
newtp->rx_opt.ts_recent_stamp = 0;
|
| 471 |
|
|
newtp->tcp_header_len = sizeof(struct tcphdr);
|
| 472 |
|
|
}
|
| 473 |
|
|
#ifdef CONFIG_TCP_MD5SIG
|
| 474 |
|
|
newtp->md5sig_info = NULL; /*XXX*/
|
| 475 |
|
|
if (newtp->af_specific->md5_lookup(sk, newsk))
|
| 476 |
|
|
newtp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
|
| 477 |
|
|
#endif
|
| 478 |
|
|
if (skb->len >= TCP_MIN_RCVMSS+newtp->tcp_header_len)
|
| 479 |
|
|
newicsk->icsk_ack.last_seg_size = skb->len - newtp->tcp_header_len;
|
| 480 |
|
|
newtp->rx_opt.mss_clamp = req->mss;
|
| 481 |
|
|
TCP_ECN_openreq_child(newtp, req);
|
| 482 |
|
|
|
| 483 |
|
|
TCP_INC_STATS_BH(TCP_MIB_PASSIVEOPENS);
|
| 484 |
|
|
}
|
| 485 |
|
|
return newsk;
|
| 486 |
|
|
}
|
| 487 |
|
|
|
| 488 |
|
|
/*
|
| 489 |
|
|
* Process an incoming packet for SYN_RECV sockets represented
|
| 490 |
|
|
* as a request_sock.
|
| 491 |
|
|
*/
|
| 492 |
|
|
|
| 493 |
|
|
struct sock *tcp_check_req(struct sock *sk,struct sk_buff *skb,
|
| 494 |
|
|
struct request_sock *req,
|
| 495 |
|
|
struct request_sock **prev)
|
| 496 |
|
|
{
|
| 497 |
|
|
const struct tcphdr *th = tcp_hdr(skb);
|
| 498 |
|
|
__be32 flg = tcp_flag_word(th) & (TCP_FLAG_RST|TCP_FLAG_SYN|TCP_FLAG_ACK);
|
| 499 |
|
|
int paws_reject = 0;
|
| 500 |
|
|
struct tcp_options_received tmp_opt;
|
| 501 |
|
|
struct sock *child;
|
| 502 |
|
|
|
| 503 |
|
|
tmp_opt.saw_tstamp = 0;
|
| 504 |
|
|
if (th->doff > (sizeof(struct tcphdr)>>2)) {
|
| 505 |
|
|
tcp_parse_options(skb, &tmp_opt, 0);
|
| 506 |
|
|
|
| 507 |
|
|
if (tmp_opt.saw_tstamp) {
|
| 508 |
|
|
tmp_opt.ts_recent = req->ts_recent;
|
| 509 |
|
|
/* We do not store true stamp, but it is not required,
|
| 510 |
|
|
* it can be estimated (approximately)
|
| 511 |
|
|
* from another data.
|
| 512 |
|
|
*/
|
| 513 |
|
|
tmp_opt.ts_recent_stamp = get_seconds() - ((TCP_TIMEOUT_INIT/HZ)<<req->retrans);
|
| 514 |
|
|
paws_reject = tcp_paws_check(&tmp_opt, th->rst);
|
| 515 |
|
|
}
|
| 516 |
|
|
}
|
| 517 |
|
|
|
| 518 |
|
|
/* Check for pure retransmitted SYN. */
|
| 519 |
|
|
if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn &&
|
| 520 |
|
|
flg == TCP_FLAG_SYN &&
|
| 521 |
|
|
!paws_reject) {
|
| 522 |
|
|
/*
|
| 523 |
|
|
* RFC793 draws (Incorrectly! It was fixed in RFC1122)
|
| 524 |
|
|
* this case on figure 6 and figure 8, but formal
|
| 525 |
|
|
* protocol description says NOTHING.
|
| 526 |
|
|
* To be more exact, it says that we should send ACK,
|
| 527 |
|
|
* because this segment (at least, if it has no data)
|
| 528 |
|
|
* is out of window.
|
| 529 |
|
|
*
|
| 530 |
|
|
* CONCLUSION: RFC793 (even with RFC1122) DOES NOT
|
| 531 |
|
|
* describe SYN-RECV state. All the description
|
| 532 |
|
|
* is wrong, we cannot believe to it and should
|
| 533 |
|
|
* rely only on common sense and implementation
|
| 534 |
|
|
* experience.
|
| 535 |
|
|
*
|
| 536 |
|
|
* Enforce "SYN-ACK" according to figure 8, figure 6
|
| 537 |
|
|
* of RFC793, fixed by RFC1122.
|
| 538 |
|
|
*/
|
| 539 |
|
|
req->rsk_ops->rtx_syn_ack(sk, req, NULL);
|
| 540 |
|
|
return NULL;
|
| 541 |
|
|
}
|
| 542 |
|
|
|
| 543 |
|
|
/* Further reproduces section "SEGMENT ARRIVES"
|
| 544 |
|
|
for state SYN-RECEIVED of RFC793.
|
| 545 |
|
|
It is broken, however, it does not work only
|
| 546 |
|
|
when SYNs are crossed.
|
| 547 |
|
|
|
| 548 |
|
|
You would think that SYN crossing is impossible here, since
|
| 549 |
|
|
we should have a SYN_SENT socket (from connect()) on our end,
|
| 550 |
|
|
but this is not true if the crossed SYNs were sent to both
|
| 551 |
|
|
ends by a malicious third party. We must defend against this,
|
| 552 |
|
|
and to do that we first verify the ACK (as per RFC793, page
|
| 553 |
|
|
36) and reset if it is invalid. Is this a true full defense?
|
| 554 |
|
|
To convince ourselves, let us consider a way in which the ACK
|
| 555 |
|
|
test can still pass in this 'malicious crossed SYNs' case.
|
| 556 |
|
|
Malicious sender sends identical SYNs (and thus identical sequence
|
| 557 |
|
|
numbers) to both A and B:
|
| 558 |
|
|
|
| 559 |
|
|
A: gets SYN, seq=7
|
| 560 |
|
|
B: gets SYN, seq=7
|
| 561 |
|
|
|
| 562 |
|
|
By our good fortune, both A and B select the same initial
|
| 563 |
|
|
send sequence number of seven :-)
|
| 564 |
|
|
|
| 565 |
|
|
A: sends SYN|ACK, seq=7, ack_seq=8
|
| 566 |
|
|
B: sends SYN|ACK, seq=7, ack_seq=8
|
| 567 |
|
|
|
| 568 |
|
|
So we are now A eating this SYN|ACK, ACK test passes. So
|
| 569 |
|
|
does sequence test, SYN is truncated, and thus we consider
|
| 570 |
|
|
it a bare ACK.
|
| 571 |
|
|
|
| 572 |
|
|
If icsk->icsk_accept_queue.rskq_defer_accept, we silently drop this
|
| 573 |
|
|
bare ACK. Otherwise, we create an established connection. Both
|
| 574 |
|
|
ends (listening sockets) accept the new incoming connection and try
|
| 575 |
|
|
to talk to each other. 8-)
|
| 576 |
|
|
|
| 577 |
|
|
Note: This case is both harmless, and rare. Possibility is about the
|
| 578 |
|
|
same as us discovering intelligent life on another plant tomorrow.
|
| 579 |
|
|
|
| 580 |
|
|
But generally, we should (RFC lies!) to accept ACK
|
| 581 |
|
|
from SYNACK both here and in tcp_rcv_state_process().
|
| 582 |
|
|
tcp_rcv_state_process() does not, hence, we do not too.
|
| 583 |
|
|
|
| 584 |
|
|
Note that the case is absolutely generic:
|
| 585 |
|
|
we cannot optimize anything here without
|
| 586 |
|
|
violating protocol. All the checks must be made
|
| 587 |
|
|
before attempt to create socket.
|
| 588 |
|
|
*/
|
| 589 |
|
|
|
| 590 |
|
|
/* RFC793 page 36: "If the connection is in any non-synchronized state ...
|
| 591 |
|
|
* and the incoming segment acknowledges something not yet
|
| 592 |
|
|
* sent (the segment carries an unacceptable ACK) ...
|
| 593 |
|
|
* a reset is sent."
|
| 594 |
|
|
*
|
| 595 |
|
|
* Invalid ACK: reset will be sent by listening socket
|
| 596 |
|
|
*/
|
| 597 |
|
|
if ((flg & TCP_FLAG_ACK) &&
|
| 598 |
|
|
(TCP_SKB_CB(skb)->ack_seq != tcp_rsk(req)->snt_isn + 1))
|
| 599 |
|
|
return sk;
|
| 600 |
|
|
|
| 601 |
|
|
/* Also, it would be not so bad idea to check rcv_tsecr, which
|
| 602 |
|
|
* is essentially ACK extension and too early or too late values
|
| 603 |
|
|
* should cause reset in unsynchronized states.
|
| 604 |
|
|
*/
|
| 605 |
|
|
|
| 606 |
|
|
/* RFC793: "first check sequence number". */
|
| 607 |
|
|
|
| 608 |
|
|
if (paws_reject || !tcp_in_window(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq,
|
| 609 |
|
|
tcp_rsk(req)->rcv_isn + 1, tcp_rsk(req)->rcv_isn + 1 + req->rcv_wnd)) {
|
| 610 |
|
|
/* Out of window: send ACK and drop. */
|
| 611 |
|
|
if (!(flg & TCP_FLAG_RST))
|
| 612 |
|
|
req->rsk_ops->send_ack(skb, req);
|
| 613 |
|
|
if (paws_reject)
|
| 614 |
|
|
NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
|
| 615 |
|
|
return NULL;
|
| 616 |
|
|
}
|
| 617 |
|
|
|
| 618 |
|
|
/* In sequence, PAWS is OK. */
|
| 619 |
|
|
|
| 620 |
|
|
if (tmp_opt.saw_tstamp && !after(TCP_SKB_CB(skb)->seq, tcp_rsk(req)->rcv_isn + 1))
|
| 621 |
|
|
req->ts_recent = tmp_opt.rcv_tsval;
|
| 622 |
|
|
|
| 623 |
|
|
if (TCP_SKB_CB(skb)->seq == tcp_rsk(req)->rcv_isn) {
|
| 624 |
|
|
/* Truncate SYN, it is out of window starting
|
| 625 |
|
|
at tcp_rsk(req)->rcv_isn + 1. */
|
| 626 |
|
|
flg &= ~TCP_FLAG_SYN;
|
| 627 |
|
|
}
|
| 628 |
|
|
|
| 629 |
|
|
/* RFC793: "second check the RST bit" and
|
| 630 |
|
|
* "fourth, check the SYN bit"
|
| 631 |
|
|
*/
|
| 632 |
|
|
if (flg & (TCP_FLAG_RST|TCP_FLAG_SYN)) {
|
| 633 |
|
|
TCP_INC_STATS_BH(TCP_MIB_ATTEMPTFAILS);
|
| 634 |
|
|
goto embryonic_reset;
|
| 635 |
|
|
}
|
| 636 |
|
|
|
| 637 |
|
|
/* ACK sequence verified above, just make sure ACK is
|
| 638 |
|
|
* set. If ACK not set, just silently drop the packet.
|
| 639 |
|
|
*/
|
| 640 |
|
|
if (!(flg & TCP_FLAG_ACK))
|
| 641 |
|
|
return NULL;
|
| 642 |
|
|
|
| 643 |
|
|
/* If TCP_DEFER_ACCEPT is set, drop bare ACK. */
|
| 644 |
|
|
if (inet_csk(sk)->icsk_accept_queue.rskq_defer_accept &&
|
| 645 |
|
|
TCP_SKB_CB(skb)->end_seq == tcp_rsk(req)->rcv_isn + 1) {
|
| 646 |
|
|
inet_rsk(req)->acked = 1;
|
| 647 |
|
|
return NULL;
|
| 648 |
|
|
}
|
| 649 |
|
|
|
| 650 |
|
|
/* OK, ACK is valid, create big socket and
|
| 651 |
|
|
* feed this segment to it. It will repeat all
|
| 652 |
|
|
* the tests. THIS SEGMENT MUST MOVE SOCKET TO
|
| 653 |
|
|
* ESTABLISHED STATE. If it will be dropped after
|
| 654 |
|
|
* socket is created, wait for troubles.
|
| 655 |
|
|
*/
|
| 656 |
|
|
child = inet_csk(sk)->icsk_af_ops->syn_recv_sock(sk, skb,
|
| 657 |
|
|
req, NULL);
|
| 658 |
|
|
if (child == NULL)
|
| 659 |
|
|
goto listen_overflow;
|
| 660 |
|
|
#ifdef CONFIG_TCP_MD5SIG
|
| 661 |
|
|
else {
|
| 662 |
|
|
/* Copy over the MD5 key from the original socket */
|
| 663 |
|
|
struct tcp_md5sig_key *key;
|
| 664 |
|
|
struct tcp_sock *tp = tcp_sk(sk);
|
| 665 |
|
|
key = tp->af_specific->md5_lookup(sk, child);
|
| 666 |
|
|
if (key != NULL) {
|
| 667 |
|
|
/*
|
| 668 |
|
|
* We're using one, so create a matching key on the
|
| 669 |
|
|
* newsk structure. If we fail to get memory then we
|
| 670 |
|
|
* end up not copying the key across. Shucks.
|
| 671 |
|
|
*/
|
| 672 |
|
|
char *newkey = kmemdup(key->key, key->keylen,
|
| 673 |
|
|
GFP_ATOMIC);
|
| 674 |
|
|
if (newkey) {
|
| 675 |
|
|
if (!tcp_alloc_md5sig_pool())
|
| 676 |
|
|
BUG();
|
| 677 |
|
|
tp->af_specific->md5_add(child, child,
|
| 678 |
|
|
newkey,
|
| 679 |
|
|
key->keylen);
|
| 680 |
|
|
}
|
| 681 |
|
|
}
|
| 682 |
|
|
}
|
| 683 |
|
|
#endif
|
| 684 |
|
|
|
| 685 |
|
|
inet_csk_reqsk_queue_unlink(sk, req, prev);
|
| 686 |
|
|
inet_csk_reqsk_queue_removed(sk, req);
|
| 687 |
|
|
|
| 688 |
|
|
inet_csk_reqsk_queue_add(sk, req, child);
|
| 689 |
|
|
return child;
|
| 690 |
|
|
|
| 691 |
|
|
listen_overflow:
|
| 692 |
|
|
if (!sysctl_tcp_abort_on_overflow) {
|
| 693 |
|
|
inet_rsk(req)->acked = 1;
|
| 694 |
|
|
return NULL;
|
| 695 |
|
|
}
|
| 696 |
|
|
|
| 697 |
|
|
embryonic_reset:
|
| 698 |
|
|
NET_INC_STATS_BH(LINUX_MIB_EMBRYONICRSTS);
|
| 699 |
|
|
if (!(flg & TCP_FLAG_RST))
|
| 700 |
|
|
req->rsk_ops->send_reset(sk, skb);
|
| 701 |
|
|
|
| 702 |
|
|
inet_csk_reqsk_queue_drop(sk, req, prev);
|
| 703 |
|
|
return NULL;
|
| 704 |
|
|
}
|
| 705 |
|
|
|
| 706 |
|
|
/*
|
| 707 |
|
|
* Queue segment on the new socket if the new socket is active,
|
| 708 |
|
|
* otherwise we just shortcircuit this and continue with
|
| 709 |
|
|
* the new socket.
|
| 710 |
|
|
*/
|
| 711 |
|
|
|
| 712 |
|
|
int tcp_child_process(struct sock *parent, struct sock *child,
|
| 713 |
|
|
struct sk_buff *skb)
|
| 714 |
|
|
{
|
| 715 |
|
|
int ret = 0;
|
| 716 |
|
|
int state = child->sk_state;
|
| 717 |
|
|
|
| 718 |
|
|
if (!sock_owned_by_user(child)) {
|
| 719 |
|
|
ret = tcp_rcv_state_process(child, skb, tcp_hdr(skb),
|
| 720 |
|
|
skb->len);
|
| 721 |
|
|
/* Wakeup parent, send SIGIO */
|
| 722 |
|
|
if (state == TCP_SYN_RECV && child->sk_state != state)
|
| 723 |
|
|
parent->sk_data_ready(parent, 0);
|
| 724 |
|
|
} else {
|
| 725 |
|
|
/* Alas, it is possible again, because we do lookup
|
| 726 |
|
|
* in main socket hash table and lock on listening
|
| 727 |
|
|
* socket does not protect us more.
|
| 728 |
|
|
*/
|
| 729 |
|
|
sk_add_backlog(child, skb);
|
| 730 |
|
|
}
|
| 731 |
|
|
|
| 732 |
|
|
bh_unlock_sock(child);
|
| 733 |
|
|
sock_put(child);
|
| 734 |
|
|
return ret;
|
| 735 |
|
|
}
|
| 736 |
|
|
|
| 737 |
|
|
EXPORT_SYMBOL(tcp_check_req);
|
| 738 |
|
|
EXPORT_SYMBOL(tcp_child_process);
|
| 739 |
|
|
EXPORT_SYMBOL(tcp_create_openreq_child);
|
| 740 |
|
|
EXPORT_SYMBOL(tcp_timewait_state_process);
|
