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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Syncookies implementation for the Linux kernel
3 *
4 * Copyright (C) 1997 Andi Kleen
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09005 * Based on ideas by D.J.Bernstein and Eric Schenk.
Linus Torvalds1da177e2005-04-16 15:20:36 -07006 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version
10 * 2 of the License, or (at your option) any later version.
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 */
12
13#include <linux/tcp.h>
14#include <linux/slab.h>
15#include <linux/random.h>
Jason A. Donenfeldfe62d052017-01-08 13:54:03 +010016#include <linux/siphash.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070017#include <linux/kernel.h>
Paul Gortmakerbc3b2d72011-07-15 11:47:34 -040018#include <linux/export.h>
Eric Dumazet84b114b2017-05-05 06:56:54 -070019#include <net/secure_seq.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070020#include <net/tcp.h>
KOVACS Krisztian86b08d82008-10-01 07:44:42 -070021#include <net/route.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070022
Jason A. Donenfeldfe62d052017-01-08 13:54:03 +010023static siphash_key_t syncookie_secret[2] __read_mostly;
Linus Torvalds1da177e2005-04-16 15:20:36 -070024
25#define COOKIEBITS 24 /* Upper bits store count */
26#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
27
Florian Westphal274e2da2014-11-03 17:35:01 +010028/* TCP Timestamp: 6 lowest bits of timestamp sent in the cookie SYN-ACK
29 * stores TCP options:
30 *
31 * MSB LSB
32 * | 31 ... 6 | 5 | 4 | 3 2 1 0 |
33 * | Timestamp | ECN | SACK | WScale |
34 *
35 * When we receive a valid cookie-ACK, we look at the echoed tsval (if
36 * any) to figure out which TCP options we should use for the rebuilt
37 * connection.
38 *
39 * A WScale setting of '0xf' (which is an invalid scaling value)
40 * means that original syn did not include the TCP window scaling option.
41 */
42#define TS_OPT_WSCALE_MASK 0xf
43#define TS_OPT_SACK BIT(4)
44#define TS_OPT_ECN BIT(5)
45/* There is no TS_OPT_TIMESTAMP:
46 * if ACK contains timestamp option, we already know it was
47 * requested/supported by the syn/synack exchange.
48 */
49#define TSBITS 6
50#define TSMASK (((__u32)1 << TSBITS) - 1)
51
Al Viro714e85b2006-11-14 20:51:49 -080052static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
Linus Torvalds1da177e2005-04-16 15:20:36 -070053 u32 count, int c)
54{
Hannes Frederic Sowab23a0022013-10-19 21:48:56 +020055 net_get_random_once(syncookie_secret, sizeof(syncookie_secret));
Jason A. Donenfeldfe62d052017-01-08 13:54:03 +010056 return siphash_4u32((__force u32)saddr, (__force u32)daddr,
57 (__force u32)sport << 16 | (__force u32)dport,
58 count, &syncookie_secret[c]);
Linus Torvalds1da177e2005-04-16 15:20:36 -070059}
60
Florian Westphal4dfc2812008-04-10 03:12:40 -070061
62/*
63 * when syncookies are in effect and tcp timestamps are enabled we encode
Florian Westphal734f6142010-06-21 11:48:44 +000064 * tcp options in the lower bits of the timestamp value that will be
Florian Westphal4dfc2812008-04-10 03:12:40 -070065 * sent in the syn-ack.
66 * Since subsequent timestamps use the normal tcp_time_stamp value, we
67 * must make sure that the resulting initial timestamp is <= tcp_time_stamp.
68 */
Eric Dumazet9a568de2017-05-16 14:00:14 -070069u64 cookie_init_timestamp(struct request_sock *req)
Florian Westphal4dfc2812008-04-10 03:12:40 -070070{
71 struct inet_request_sock *ireq;
Eric Dumazet9a568de2017-05-16 14:00:14 -070072 u32 ts, ts_now = tcp_time_stamp_raw();
Florian Westphal4dfc2812008-04-10 03:12:40 -070073 u32 options = 0;
74
75 ireq = inet_rsk(req);
Florian Westphal734f6142010-06-21 11:48:44 +000076
Florian Westphal274e2da2014-11-03 17:35:01 +010077 options = ireq->wscale_ok ? ireq->snd_wscale : TS_OPT_WSCALE_MASK;
78 if (ireq->sack_ok)
79 options |= TS_OPT_SACK;
80 if (ireq->ecn_ok)
81 options |= TS_OPT_ECN;
Florian Westphal4dfc2812008-04-10 03:12:40 -070082
83 ts = ts_now & ~TSMASK;
84 ts |= options;
85 if (ts > ts_now) {
86 ts >>= TSBITS;
87 ts--;
88 ts <<= TSBITS;
89 ts |= options;
90 }
Eric Dumazet9a568de2017-05-16 14:00:14 -070091 return (u64)ts * (USEC_PER_SEC / TCP_TS_HZ);
Florian Westphal4dfc2812008-04-10 03:12:40 -070092}
93
94
Al Viro714e85b2006-11-14 20:51:49 -080095static __u32 secure_tcp_syn_cookie(__be32 saddr, __be32 daddr, __be16 sport,
Florian Westphal8c27bd72013-09-20 22:32:55 +020096 __be16 dport, __u32 sseq, __u32 data)
Linus Torvalds1da177e2005-04-16 15:20:36 -070097{
98 /*
99 * Compute the secure sequence number.
100 * The output should be:
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900101 * HASH(sec1,saddr,sport,daddr,dport,sec1) + sseq + (count * 2^24)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 * + (HASH(sec2,saddr,sport,daddr,dport,count,sec2) % 2^24).
103 * Where sseq is their sequence number and count increases every
104 * minute by 1.
105 * As an extra hack, we add a small "data" value that encodes the
106 * MSS into the second hash value.
107 */
Florian Westphal8c27bd72013-09-20 22:32:55 +0200108 u32 count = tcp_cookie_time();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 return (cookie_hash(saddr, daddr, sport, dport, 0, 0) +
110 sseq + (count << COOKIEBITS) +
111 ((cookie_hash(saddr, daddr, sport, dport, count, 1) + data)
112 & COOKIEMASK));
113}
114
115/*
116 * This retrieves the small "data" value from the syncookie.
117 * If the syncookie is bad, the data returned will be out of
118 * range. This must be checked by the caller.
119 *
Florian Westphal8c27bd72013-09-20 22:32:55 +0200120 * The count value used to generate the cookie must be less than
121 * MAX_SYNCOOKIE_AGE minutes in the past.
122 * The return value (__u32)-1 if this test fails.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700123 */
Al Viro714e85b2006-11-14 20:51:49 -0800124static __u32 check_tcp_syn_cookie(__u32 cookie, __be32 saddr, __be32 daddr,
Florian Westphal8c27bd72013-09-20 22:32:55 +0200125 __be16 sport, __be16 dport, __u32 sseq)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700126{
Florian Westphal8c27bd72013-09-20 22:32:55 +0200127 u32 diff, count = tcp_cookie_time();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128
129 /* Strip away the layers from the cookie */
130 cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
131
132 /* Cookie is now reduced to (count * 2^24) ^ (hash % 2^24) */
Weilong Chen0c9a67d2013-12-23 14:37:27 +0800133 diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS);
Florian Westphal8c27bd72013-09-20 22:32:55 +0200134 if (diff >= MAX_SYNCOOKIE_AGE)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135 return (__u32)-1;
136
137 return (cookie -
138 cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
139 & COOKIEMASK; /* Leaving the data behind */
140}
141
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900142/*
Florian Westphal08629352013-09-20 22:32:56 +0200143 * MSS Values are chosen based on the 2011 paper
144 * 'An Analysis of TCP Maximum Segement Sizes' by S. Alcock and R. Nelson.
145 * Values ..
146 * .. lower than 536 are rare (< 0.2%)
147 * .. between 537 and 1299 account for less than < 1.5% of observed values
148 * .. in the 1300-1349 range account for about 15 to 20% of observed mss values
149 * .. exceeding 1460 are very rare (< 0.04%)
Florian Westphal5918e2f2010-06-03 00:43:57 +0000150 *
Florian Westphal08629352013-09-20 22:32:56 +0200151 * 1460 is the single most frequently announced mss value (30 to 46% depending
152 * on monitor location). Table must be sorted.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153 */
154static __u16 const msstab[] = {
Florian Westphal5918e2f2010-06-03 00:43:57 +0000155 536,
Florian Westphal08629352013-09-20 22:32:56 +0200156 1300,
157 1440, /* 1440, 1452: PPPoE */
Florian Westphal5918e2f2010-06-03 00:43:57 +0000158 1460,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159};
Linus Torvalds1da177e2005-04-16 15:20:36 -0700160
161/*
162 * Generate a syncookie. mssp points to the mss, which is returned
163 * rounded down to the value encoded in the cookie.
164 */
Patrick McHardy01982302013-08-27 08:50:13 +0200165u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
166 u16 *mssp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700167{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168 int mssind;
169 const __u16 mss = *mssp;
170
Florian Westphal5918e2f2010-06-03 00:43:57 +0000171 for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
172 if (mss >= msstab[mssind])
173 break;
174 *mssp = msstab[mssind];
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -0700176 return secure_tcp_syn_cookie(iph->saddr, iph->daddr,
177 th->source, th->dest, ntohl(th->seq),
Florian Westphal8c27bd72013-09-20 22:32:55 +0200178 mssind);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700179}
Patrick McHardy01982302013-08-27 08:50:13 +0200180EXPORT_SYMBOL_GPL(__cookie_v4_init_sequence);
181
Eric Dumazet3f684b42015-09-29 07:42:49 -0700182__u32 cookie_v4_init_sequence(const struct sk_buff *skb, __u16 *mssp)
Patrick McHardy01982302013-08-27 08:50:13 +0200183{
184 const struct iphdr *iph = ip_hdr(skb);
185 const struct tcphdr *th = tcp_hdr(skb);
186
Patrick McHardy01982302013-08-27 08:50:13 +0200187 return __cookie_v4_init_sequence(iph, th, mssp);
188}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900190/*
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900191 * Check if a ack sequence number is a valid syncookie.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700192 * Return the decoded mss if it is, or 0 if not.
193 */
Patrick McHardy01982302013-08-27 08:50:13 +0200194int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
195 u32 cookie)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700196{
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -0700197 __u32 seq = ntohl(th->seq) - 1;
198 __u32 mssind = check_tcp_syn_cookie(cookie, iph->saddr, iph->daddr,
Florian Westphal8c27bd72013-09-20 22:32:55 +0200199 th->source, th->dest, seq);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700200
Florian Westphal5918e2f2010-06-03 00:43:57 +0000201 return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202}
Patrick McHardy01982302013-08-27 08:50:13 +0200203EXPORT_SYMBOL_GPL(__cookie_v4_check);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700204
Eric Dumazetb80c0e72015-06-04 18:30:43 -0700205struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
206 struct request_sock *req,
Eric Dumazet84b114b2017-05-05 06:56:54 -0700207 struct dst_entry *dst, u32 tsoff)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700208{
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -0800209 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210 struct sock *child;
Eric Dumazet5e0724d2015-10-22 08:20:46 -0700211 bool own_req;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700212
Eric Dumazet5e0724d2015-10-22 08:20:46 -0700213 child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst,
214 NULL, &own_req);
Eric Dumazet0470c8c2015-03-17 18:32:31 -0700215 if (child) {
Reshetova, Elena41c6d652017-06-30 13:08:01 +0300216 refcount_set(&req->rsk_refcnt, 1);
Eric Dumazet84b114b2017-05-05 06:56:54 -0700217 tcp_sk(child)->tsoffset = tsoff;
Eric Dumazet6bcfd7f2015-10-08 11:16:48 -0700218 sock_rps_save_rxhash(child, skb);
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700219 inet_csk_reqsk_queue_add(sk, req, child);
Eric Dumazet0470c8c2015-03-17 18:32:31 -0700220 } else {
Arnaldo Carvalho de Melo60236fd2005-06-18 22:47:21 -0700221 reqsk_free(req);
Eric Dumazet0470c8c2015-03-17 18:32:31 -0700222 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700223 return child;
224}
Eric Dumazetb80c0e72015-06-04 18:30:43 -0700225EXPORT_SYMBOL(tcp_get_cookie_sock);
Florian Westphal4dfc2812008-04-10 03:12:40 -0700226
227/*
228 * when syncookies are in effect and tcp timestamps are enabled we stored
229 * additional tcp options in the timestamp.
230 * This extracts these options from the timestamp echo.
231 *
Florian Westphalf1673382014-11-03 17:35:02 +0100232 * return false if we decode a tcp option that is disabled
233 * on the host.
Florian Westphal4dfc2812008-04-10 03:12:40 -0700234 */
Eric Dumazetf9301032017-06-07 10:34:37 -0700235bool cookie_timestamp_decode(const struct net *net,
236 struct tcp_options_received *tcp_opt)
Florian Westphal4dfc2812008-04-10 03:12:40 -0700237{
Florian Westphal734f6142010-06-21 11:48:44 +0000238 /* echoed timestamp, lowest bits contain options */
Florian Westphal274e2da2014-11-03 17:35:01 +0100239 u32 options = tcp_opt->rcv_tsecr;
Florian Westphal4dfc2812008-04-10 03:12:40 -0700240
Florian Westphal8c763682010-06-16 14:42:15 -0700241 if (!tcp_opt->saw_tstamp) {
242 tcp_clear_options(tcp_opt);
243 return true;
244 }
245
Eric Dumazet5d2ed052017-06-07 10:34:39 -0700246 if (!net->ipv4.sysctl_tcp_timestamps)
Florian Westphal8c763682010-06-16 14:42:15 -0700247 return false;
248
Florian Westphal274e2da2014-11-03 17:35:01 +0100249 tcp_opt->sack_ok = (options & TS_OPT_SACK) ? TCP_SACK_SEEN : 0;
Florian Westphal4dfc2812008-04-10 03:12:40 -0700250
Eric Dumazetf9301032017-06-07 10:34:37 -0700251 if (tcp_opt->sack_ok && !net->ipv4.sysctl_tcp_sack)
Florian Westphal8c763682010-06-16 14:42:15 -0700252 return false;
Florian Westphal4dfc2812008-04-10 03:12:40 -0700253
Florian Westphal274e2da2014-11-03 17:35:01 +0100254 if ((options & TS_OPT_WSCALE_MASK) == TS_OPT_WSCALE_MASK)
Florian Westphal734f6142010-06-21 11:48:44 +0000255 return true; /* no window scaling */
256
257 tcp_opt->wscale_ok = 1;
Florian Westphal274e2da2014-11-03 17:35:01 +0100258 tcp_opt->snd_wscale = options & TS_OPT_WSCALE_MASK;
259
Eric Dumazet9bb37ef2017-06-07 10:34:38 -0700260 return net->ipv4.sysctl_tcp_window_scaling != 0;
Florian Westphal4dfc2812008-04-10 03:12:40 -0700261}
Florian Westphalf1673382014-11-03 17:35:02 +0100262EXPORT_SYMBOL(cookie_timestamp_decode);
263
264bool cookie_ecn_ok(const struct tcp_options_received *tcp_opt,
Florian Westphalf7b3bec2014-11-03 17:35:03 +0100265 const struct net *net, const struct dst_entry *dst)
Florian Westphalf1673382014-11-03 17:35:02 +0100266{
267 bool ecn_ok = tcp_opt->rcv_tsecr & TS_OPT_ECN;
268
269 if (!ecn_ok)
270 return false;
271
272 if (net->ipv4.sysctl_tcp_ecn)
273 return true;
274
Florian Westphalf7b3bec2014-11-03 17:35:03 +0100275 return dst_feature(dst, RTAX_FEATURE_ECN);
Florian Westphalf1673382014-11-03 17:35:02 +0100276}
277EXPORT_SYMBOL(cookie_ecn_ok);
Florian Westphal4dfc2812008-04-10 03:12:40 -0700278
Eric Dumazet079096f2015-10-02 11:43:32 -0700279/* On input, sk is a listener.
280 * Output is listener if incoming packet would not create a child
281 * NULL if memory could not be allocated.
282 */
Cong Wang461b74c2014-10-15 14:33:22 -0700283struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700284{
Cong Wang461b74c2014-10-15 14:33:22 -0700285 struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
William Allen Simpson4957faade2009-12-02 18:25:27 +0000286 struct tcp_options_received tcp_opt;
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -0700287 struct inet_request_sock *ireq;
288 struct tcp_request_sock *treq;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700289 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -0700290 const struct tcphdr *th = tcp_hdr(skb);
291 __u32 cookie = ntohl(th->ack_seq) - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700292 struct sock *ret = sk;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900293 struct request_sock *req;
294 int mss;
295 struct rtable *rt;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700296 __u8 rcv_wscale;
Eric Dumazetdfd25ff2012-03-10 09:20:21 +0000297 struct flowi4 fl4;
Eric Dumazet84b114b2017-05-05 06:56:54 -0700298 u32 tsoff = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700299
Nikolay Borisov12ed8242016-02-03 09:46:51 +0200300 if (!sock_net(sk)->ipv4.sysctl_tcp_syncookies || !th->ack || th->rst)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700301 goto out;
302
Florian Westphal646697b2014-10-30 02:55:38 +0100303 if (tcp_synq_no_recent_overflow(sk))
304 goto out;
305
306 mss = __cookie_v4_check(ip_hdr(skb), th, cookie);
307 if (mss == 0) {
Eric Dumazet02a1d6e2016-04-27 16:44:39 -0700308 __NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700309 goto out;
310 }
311
Eric Dumazet02a1d6e2016-04-27 16:44:39 -0700312 __NET_INC_STATS(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700313
David S. Millerbb5b7c12009-12-15 20:56:42 -0800314 /* check for timestamp cookie support */
315 memset(&tcp_opt, 0, sizeof(tcp_opt));
Eric Dumazeteed29f12017-06-07 10:34:36 -0700316 tcp_parse_options(sock_net(sk), skb, &tcp_opt, 0, NULL);
David S. Millerbb5b7c12009-12-15 20:56:42 -0800317
Eric Dumazet84b114b2017-05-05 06:56:54 -0700318 if (tcp_opt.saw_tstamp && tcp_opt.rcv_tsecr) {
Eric Dumazet5d2ed052017-06-07 10:34:39 -0700319 tsoff = secure_tcp_ts_off(sock_net(sk),
320 ip_hdr(skb)->daddr,
321 ip_hdr(skb)->saddr);
Eric Dumazet84b114b2017-05-05 06:56:54 -0700322 tcp_opt.rcv_tsecr -= tsoff;
323 }
324
Eric Dumazetf9301032017-06-07 10:34:37 -0700325 if (!cookie_timestamp_decode(sock_net(sk), &tcp_opt))
Florian Westphal8c763682010-06-16 14:42:15 -0700326 goto out;
David S. Millerbb5b7c12009-12-15 20:56:42 -0800327
Linus Torvalds1da177e2005-04-16 15:20:36 -0700328 ret = NULL;
Eric Dumazeta1a53442015-10-04 21:08:11 -0700329 req = inet_reqsk_alloc(&tcp_request_sock_ops, sk, false); /* for safety */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700330 if (!req)
331 goto out;
332
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -0700333 ireq = inet_rsk(req);
334 treq = tcp_rsk(req);
Arnaldo Carvalho de Meloaa8223c2007-04-10 21:04:22 -0700335 treq->rcv_isn = ntohl(th->seq) - 1;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900336 treq->snt_isn = cookie;
Florian Westphal95a22ca2016-12-01 11:32:06 +0100337 treq->ts_off = 0;
Alexander Potapenko18bcf292017-07-17 12:35:58 +0200338 treq->txhash = net_tx_rndhash();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700339 req->mss = mss;
Eric Dumazetb44084c2013-10-10 00:04:37 -0700340 ireq->ir_num = ntohs(th->dest);
341 ireq->ir_rmt_port = th->source;
Eric Dumazet08d2cc3b2015-03-18 14:05:38 -0700342 sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
343 sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
Lorenzo Colitti84f39b02014-05-13 10:17:35 -0700344 ireq->ir_mark = inet_request_mark(sk, skb);
David S. Millerbb5b7c12009-12-15 20:56:42 -0800345 ireq->snd_wscale = tcp_opt.snd_wscale;
David S. Millerbb5b7c12009-12-15 20:56:42 -0800346 ireq->sack_ok = tcp_opt.sack_ok;
347 ireq->wscale_ok = tcp_opt.wscale_ok;
348 ireq->tstamp_ok = tcp_opt.saw_tstamp;
349 req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
Eric Dumazet9a568de2017-05-16 14:00:14 -0700350 treq->snt_synack = 0;
Eric Dumazet9439ce02015-03-17 18:32:29 -0700351 treq->tfo_listener = false;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700352
David Ahern6dd9a142015-12-16 13:20:44 -0800353 ireq->ir_iif = inet_request_bound_dev_if(sk, skb);
Eric Dumazet16f86162015-03-13 15:51:10 -0700354
Linus Torvalds1da177e2005-04-16 15:20:36 -0700355 /* We throwed the options of the initial SYN away, so we hope
356 * the ACK carries the same options again (see RFC1122 4.2.3.8)
357 */
Eric Dumazetc92e8c02017-10-20 09:04:13 -0700358 RCU_INIT_POINTER(ireq->ireq_opt, tcp_v4_save_options(sock_net(sk), skb));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700359
Paul Moore284904a2009-03-27 17:10:28 -0400360 if (security_inet_conn_request(sk, skb, req)) {
Eric Dumazet0470c8c2015-03-17 18:32:31 -0700361 reqsk_free(req);
Paul Moore284904a2009-03-27 17:10:28 -0400362 goto out;
363 }
364
Eric Dumazete6c022a2012-10-27 23:16:46 +0000365 req->num_retrans = 0;
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900366
Linus Torvalds1da177e2005-04-16 15:20:36 -0700367 /*
368 * We need to lookup the route here to get at the correct
369 * window size. We should better make sure that the window size
370 * hasn't changed since we received the original syn, but I see
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900371 * no easy way to do this.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700372 */
David Ahern6dd9a142015-12-16 13:20:44 -0800373 flowi4_init_output(&fl4, ireq->ir_iif, ireq->ir_mark,
Dmitry Popovd66954a2013-04-11 08:55:07 +0000374 RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE, IPPROTO_TCP,
Eric Dumazetdfd25ff2012-03-10 09:20:21 +0000375 inet_sk_flowi_flags(sk),
Cong Wang461b74c2014-10-15 14:33:22 -0700376 opt->srr ? opt->faddr : ireq->ir_rmt_addr,
Lorenzo Colittie2d118a2016-11-04 02:23:43 +0900377 ireq->ir_loc_addr, th->source, th->dest, sk->sk_uid);
Eric Dumazetdfd25ff2012-03-10 09:20:21 +0000378 security_req_classify_flow(req, flowi4_to_flowi(&fl4));
379 rt = ip_route_output_key(sock_net(sk), &fl4);
380 if (IS_ERR(rt)) {
Eric Dumazet0470c8c2015-03-17 18:32:31 -0700381 reqsk_free(req);
Eric Dumazetdfd25ff2012-03-10 09:20:21 +0000382 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700383 }
384
385 /* Try to redo what tcp_v4_send_synack did. */
Eric Dumazeted53d0a2015-10-08 19:33:23 -0700386 req->rsk_window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW);
Florian Westphal4dfc2812008-04-10 03:12:40 -0700387
Eric Dumazetceef9ab2017-10-27 07:47:24 -0700388 tcp_select_initial_window(sk, tcp_full_space(sk), req->mss,
Eric Dumazeted53d0a2015-10-08 19:33:23 -0700389 &req->rsk_rcv_wnd, &req->rsk_window_clamp,
laurent chavey31d12922009-12-15 11:15:28 +0000390 ireq->wscale_ok, &rcv_wscale,
Changli Gaod8d1f302010-06-10 23:31:35 -0700391 dst_metric(&rt->dst, RTAX_INITRWND));
Florian Westphal4dfc2812008-04-10 03:12:40 -0700392
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900393 ireq->rcv_wscale = rcv_wscale;
Florian Westphalf7b3bec2014-11-03 17:35:03 +0100394 ireq->ecn_ok = cookie_ecn_ok(&tcp_opt, sock_net(sk), &rt->dst);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700395
Eric Dumazet84b114b2017-05-05 06:56:54 -0700396 ret = tcp_get_cookie_sock(sk, skb, req, &rt->dst, tsoff);
Eric Dumazetdfd25ff2012-03-10 09:20:21 +0000397 /* ip_queue_xmit() depends on our flow being setup
398 * Normal sockets get it right from inet_csk_route_child_sock()
399 */
400 if (ret)
401 inet_sk(ret)->cork.fl.u.ip4 = fl4;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700402out: return ret;
403}