Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 1 | /* |
| 2 | * Syncookies implementation for the Linux kernel |
| 3 | * |
| 4 | * Copyright (C) 1997 Andi Kleen |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 5 | * Based on ideas by D.J.Bernstein and Eric Schenk. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 6 | * |
| 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 Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 11 | */ |
| 12 | |
| 13 | #include <linux/tcp.h> |
| 14 | #include <linux/slab.h> |
| 15 | #include <linux/random.h> |
| 16 | #include <linux/cryptohash.h> |
| 17 | #include <linux/kernel.h> |
Paul Gortmaker | bc3b2d7 | 2011-07-15 11:47:34 -0400 | [diff] [blame] | 18 | #include <linux/export.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 19 | #include <net/tcp.h> |
KOVACS Krisztian | 86b08d8 | 2008-10-01 07:44:42 -0700 | [diff] [blame] | 20 | #include <net/route.h> |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 21 | |
Florian Westphal | 734f614 | 2010-06-21 11:48:44 +0000 | [diff] [blame] | 22 | /* Timestamps: lowest bits store TCP options */ |
Florian Westphal | 172d69e | 2010-06-21 11:48:45 +0000 | [diff] [blame] | 23 | #define TSBITS 6 |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 24 | #define TSMASK (((__u32)1 << TSBITS) - 1) |
| 25 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 26 | extern int sysctl_tcp_syncookies; |
| 27 | |
Florian Westphal | 253ff51 | 2014-08-26 12:55:53 +0200 | [diff] [blame] | 28 | static u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS] __read_mostly; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 29 | |
| 30 | #define COOKIEBITS 24 /* Upper bits store count */ |
| 31 | #define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1) |
| 32 | |
Tejun Heo | 245b2e7 | 2009-06-24 15:13:48 +0900 | [diff] [blame] | 33 | static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS], |
| 34 | ipv4_cookie_scratch); |
Eric Dumazet | 11baab7 | 2008-02-07 10:40:19 +0100 | [diff] [blame] | 35 | |
Al Viro | 714e85b | 2006-11-14 20:51:49 -0800 | [diff] [blame] | 36 | static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 37 | u32 count, int c) |
| 38 | { |
Hannes Frederic Sowa | b23a002 | 2013-10-19 21:48:56 +0200 | [diff] [blame] | 39 | __u32 *tmp; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 40 | |
Hannes Frederic Sowa | b23a002 | 2013-10-19 21:48:56 +0200 | [diff] [blame] | 41 | net_get_random_once(syncookie_secret, sizeof(syncookie_secret)); |
| 42 | |
| 43 | tmp = __get_cpu_var(ipv4_cookie_scratch); |
Florian Westphal | 2051f11 | 2008-03-23 22:21:28 -0700 | [diff] [blame] | 44 | memcpy(tmp + 4, syncookie_secret[c], sizeof(syncookie_secret[c])); |
Al Viro | 714e85b | 2006-11-14 20:51:49 -0800 | [diff] [blame] | 45 | tmp[0] = (__force u32)saddr; |
| 46 | tmp[1] = (__force u32)daddr; |
| 47 | tmp[2] = ((__force u32)sport << 16) + (__force u32)dport; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 48 | tmp[3] = count; |
| 49 | sha_transform(tmp + 16, (__u8 *)tmp, tmp + 16 + 5); |
| 50 | |
| 51 | return tmp[17]; |
| 52 | } |
| 53 | |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 54 | |
| 55 | /* |
| 56 | * when syncookies are in effect and tcp timestamps are enabled we encode |
Florian Westphal | 734f614 | 2010-06-21 11:48:44 +0000 | [diff] [blame] | 57 | * tcp options in the lower bits of the timestamp value that will be |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 58 | * sent in the syn-ack. |
| 59 | * Since subsequent timestamps use the normal tcp_time_stamp value, we |
| 60 | * must make sure that the resulting initial timestamp is <= tcp_time_stamp. |
| 61 | */ |
| 62 | __u32 cookie_init_timestamp(struct request_sock *req) |
| 63 | { |
| 64 | struct inet_request_sock *ireq; |
| 65 | u32 ts, ts_now = tcp_time_stamp; |
| 66 | u32 options = 0; |
| 67 | |
| 68 | ireq = inet_rsk(req); |
Florian Westphal | 734f614 | 2010-06-21 11:48:44 +0000 | [diff] [blame] | 69 | |
| 70 | options = ireq->wscale_ok ? ireq->snd_wscale : 0xf; |
| 71 | options |= ireq->sack_ok << 4; |
Florian Westphal | 172d69e | 2010-06-21 11:48:45 +0000 | [diff] [blame] | 72 | options |= ireq->ecn_ok << 5; |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 73 | |
| 74 | ts = ts_now & ~TSMASK; |
| 75 | ts |= options; |
| 76 | if (ts > ts_now) { |
| 77 | ts >>= TSBITS; |
| 78 | ts--; |
| 79 | ts <<= TSBITS; |
| 80 | ts |= options; |
| 81 | } |
| 82 | return ts; |
| 83 | } |
| 84 | |
| 85 | |
Al Viro | 714e85b | 2006-11-14 20:51:49 -0800 | [diff] [blame] | 86 | static __u32 secure_tcp_syn_cookie(__be32 saddr, __be32 daddr, __be16 sport, |
Florian Westphal | 8c27bd7 | 2013-09-20 22:32:55 +0200 | [diff] [blame] | 87 | __be16 dport, __u32 sseq, __u32 data) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 88 | { |
| 89 | /* |
| 90 | * Compute the secure sequence number. |
| 91 | * The output should be: |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 92 | * HASH(sec1,saddr,sport,daddr,dport,sec1) + sseq + (count * 2^24) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 93 | * + (HASH(sec2,saddr,sport,daddr,dport,count,sec2) % 2^24). |
| 94 | * Where sseq is their sequence number and count increases every |
| 95 | * minute by 1. |
| 96 | * As an extra hack, we add a small "data" value that encodes the |
| 97 | * MSS into the second hash value. |
| 98 | */ |
Florian Westphal | 8c27bd7 | 2013-09-20 22:32:55 +0200 | [diff] [blame] | 99 | u32 count = tcp_cookie_time(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 100 | return (cookie_hash(saddr, daddr, sport, dport, 0, 0) + |
| 101 | sseq + (count << COOKIEBITS) + |
| 102 | ((cookie_hash(saddr, daddr, sport, dport, count, 1) + data) |
| 103 | & COOKIEMASK)); |
| 104 | } |
| 105 | |
| 106 | /* |
| 107 | * This retrieves the small "data" value from the syncookie. |
| 108 | * If the syncookie is bad, the data returned will be out of |
| 109 | * range. This must be checked by the caller. |
| 110 | * |
Florian Westphal | 8c27bd7 | 2013-09-20 22:32:55 +0200 | [diff] [blame] | 111 | * The count value used to generate the cookie must be less than |
| 112 | * MAX_SYNCOOKIE_AGE minutes in the past. |
| 113 | * The return value (__u32)-1 if this test fails. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 114 | */ |
Al Viro | 714e85b | 2006-11-14 20:51:49 -0800 | [diff] [blame] | 115 | static __u32 check_tcp_syn_cookie(__u32 cookie, __be32 saddr, __be32 daddr, |
Florian Westphal | 8c27bd7 | 2013-09-20 22:32:55 +0200 | [diff] [blame] | 116 | __be16 sport, __be16 dport, __u32 sseq) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 117 | { |
Florian Westphal | 8c27bd7 | 2013-09-20 22:32:55 +0200 | [diff] [blame] | 118 | u32 diff, count = tcp_cookie_time(); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 119 | |
| 120 | /* Strip away the layers from the cookie */ |
| 121 | cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq; |
| 122 | |
| 123 | /* Cookie is now reduced to (count * 2^24) ^ (hash % 2^24) */ |
Weilong Chen | 0c9a67d | 2013-12-23 14:37:27 +0800 | [diff] [blame] | 124 | diff = (count - (cookie >> COOKIEBITS)) & ((__u32) -1 >> COOKIEBITS); |
Florian Westphal | 8c27bd7 | 2013-09-20 22:32:55 +0200 | [diff] [blame] | 125 | if (diff >= MAX_SYNCOOKIE_AGE) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 126 | return (__u32)-1; |
| 127 | |
| 128 | return (cookie - |
| 129 | cookie_hash(saddr, daddr, sport, dport, count - diff, 1)) |
| 130 | & COOKIEMASK; /* Leaving the data behind */ |
| 131 | } |
| 132 | |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 133 | /* |
Florian Westphal | 0862935 | 2013-09-20 22:32:56 +0200 | [diff] [blame] | 134 | * MSS Values are chosen based on the 2011 paper |
| 135 | * 'An Analysis of TCP Maximum Segement Sizes' by S. Alcock and R. Nelson. |
| 136 | * Values .. |
| 137 | * .. lower than 536 are rare (< 0.2%) |
| 138 | * .. between 537 and 1299 account for less than < 1.5% of observed values |
| 139 | * .. in the 1300-1349 range account for about 15 to 20% of observed mss values |
| 140 | * .. exceeding 1460 are very rare (< 0.04%) |
Florian Westphal | 5918e2f | 2010-06-03 00:43:57 +0000 | [diff] [blame] | 141 | * |
Florian Westphal | 0862935 | 2013-09-20 22:32:56 +0200 | [diff] [blame] | 142 | * 1460 is the single most frequently announced mss value (30 to 46% depending |
| 143 | * on monitor location). Table must be sorted. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 144 | */ |
| 145 | static __u16 const msstab[] = { |
Florian Westphal | 5918e2f | 2010-06-03 00:43:57 +0000 | [diff] [blame] | 146 | 536, |
Florian Westphal | 0862935 | 2013-09-20 22:32:56 +0200 | [diff] [blame] | 147 | 1300, |
| 148 | 1440, /* 1440, 1452: PPPoE */ |
Florian Westphal | 5918e2f | 2010-06-03 00:43:57 +0000 | [diff] [blame] | 149 | 1460, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 150 | }; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 151 | |
| 152 | /* |
| 153 | * Generate a syncookie. mssp points to the mss, which is returned |
| 154 | * rounded down to the value encoded in the cookie. |
| 155 | */ |
Patrick McHardy | 0198230 | 2013-08-27 08:50:13 +0200 | [diff] [blame] | 156 | u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th, |
| 157 | u16 *mssp) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 158 | { |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 159 | int mssind; |
| 160 | const __u16 mss = *mssp; |
| 161 | |
Florian Westphal | 5918e2f | 2010-06-03 00:43:57 +0000 | [diff] [blame] | 162 | for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--) |
| 163 | if (mss >= msstab[mssind]) |
| 164 | break; |
| 165 | *mssp = msstab[mssind]; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 166 | |
Arnaldo Carvalho de Melo | aa8223c | 2007-04-10 21:04:22 -0700 | [diff] [blame] | 167 | return secure_tcp_syn_cookie(iph->saddr, iph->daddr, |
| 168 | th->source, th->dest, ntohl(th->seq), |
Florian Westphal | 8c27bd7 | 2013-09-20 22:32:55 +0200 | [diff] [blame] | 169 | mssind); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 170 | } |
Patrick McHardy | 0198230 | 2013-08-27 08:50:13 +0200 | [diff] [blame] | 171 | EXPORT_SYMBOL_GPL(__cookie_v4_init_sequence); |
| 172 | |
Octavian Purdila | 57b4755 | 2014-06-25 17:09:50 +0300 | [diff] [blame] | 173 | __u32 cookie_v4_init_sequence(struct sock *sk, const struct sk_buff *skb, |
| 174 | __u16 *mssp) |
Patrick McHardy | 0198230 | 2013-08-27 08:50:13 +0200 | [diff] [blame] | 175 | { |
| 176 | const struct iphdr *iph = ip_hdr(skb); |
| 177 | const struct tcphdr *th = tcp_hdr(skb); |
| 178 | |
| 179 | tcp_synq_overflow(sk); |
| 180 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT); |
| 181 | |
| 182 | return __cookie_v4_init_sequence(iph, th, mssp); |
| 183 | } |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 184 | |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 185 | /* |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 186 | * Check if a ack sequence number is a valid syncookie. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 187 | * Return the decoded mss if it is, or 0 if not. |
| 188 | */ |
Patrick McHardy | 0198230 | 2013-08-27 08:50:13 +0200 | [diff] [blame] | 189 | int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th, |
| 190 | u32 cookie) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 191 | { |
Arnaldo Carvalho de Melo | aa8223c | 2007-04-10 21:04:22 -0700 | [diff] [blame] | 192 | __u32 seq = ntohl(th->seq) - 1; |
| 193 | __u32 mssind = check_tcp_syn_cookie(cookie, iph->saddr, iph->daddr, |
Florian Westphal | 8c27bd7 | 2013-09-20 22:32:55 +0200 | [diff] [blame] | 194 | th->source, th->dest, seq); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 195 | |
Florian Westphal | 5918e2f | 2010-06-03 00:43:57 +0000 | [diff] [blame] | 196 | return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 197 | } |
Patrick McHardy | 0198230 | 2013-08-27 08:50:13 +0200 | [diff] [blame] | 198 | EXPORT_SYMBOL_GPL(__cookie_v4_check); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 199 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 200 | static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb, |
Arnaldo Carvalho de Melo | 60236fd | 2005-06-18 22:47:21 -0700 | [diff] [blame] | 201 | struct request_sock *req, |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 202 | struct dst_entry *dst) |
| 203 | { |
Arnaldo Carvalho de Melo | 8292a17 | 2005-12-13 23:15:52 -0800 | [diff] [blame] | 204 | struct inet_connection_sock *icsk = inet_csk(sk); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 205 | struct sock *child; |
| 206 | |
Arnaldo Carvalho de Melo | 8292a17 | 2005-12-13 23:15:52 -0800 | [diff] [blame] | 207 | child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 208 | if (child) |
Arnaldo Carvalho de Melo | 463c84b | 2005-08-09 20:10:42 -0700 | [diff] [blame] | 209 | inet_csk_reqsk_queue_add(sk, req, child); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 210 | else |
Arnaldo Carvalho de Melo | 60236fd | 2005-06-18 22:47:21 -0700 | [diff] [blame] | 211 | reqsk_free(req); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 212 | |
| 213 | return child; |
| 214 | } |
| 215 | |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 216 | |
| 217 | /* |
| 218 | * when syncookies are in effect and tcp timestamps are enabled we stored |
| 219 | * additional tcp options in the timestamp. |
| 220 | * This extracts these options from the timestamp echo. |
| 221 | * |
Florian Westphal | 734f614 | 2010-06-21 11:48:44 +0000 | [diff] [blame] | 222 | * The lowest 4 bits store snd_wscale. |
Florian Westphal | 172d69e | 2010-06-21 11:48:45 +0000 | [diff] [blame] | 223 | * next 2 bits indicate SACK and ECN support. |
Florian Westphal | 8c76368 | 2010-06-16 14:42:15 -0700 | [diff] [blame] | 224 | * |
| 225 | * return false if we decode an option that should not be. |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 226 | */ |
Hannes Frederic Sowa | 5d134f1 | 2013-01-05 16:10:48 +0000 | [diff] [blame] | 227 | bool cookie_check_timestamp(struct tcp_options_received *tcp_opt, |
| 228 | struct net *net, bool *ecn_ok) |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 229 | { |
Florian Westphal | 734f614 | 2010-06-21 11:48:44 +0000 | [diff] [blame] | 230 | /* echoed timestamp, lowest bits contain options */ |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 231 | u32 options = tcp_opt->rcv_tsecr & TSMASK; |
| 232 | |
Florian Westphal | 8c76368 | 2010-06-16 14:42:15 -0700 | [diff] [blame] | 233 | if (!tcp_opt->saw_tstamp) { |
| 234 | tcp_clear_options(tcp_opt); |
| 235 | return true; |
| 236 | } |
| 237 | |
| 238 | if (!sysctl_tcp_timestamps) |
| 239 | return false; |
| 240 | |
Vijay Subramanian | ab56222 | 2011-12-20 13:23:24 +0000 | [diff] [blame] | 241 | tcp_opt->sack_ok = (options & (1 << 4)) ? TCP_SACK_SEEN : 0; |
Florian Westphal | 172d69e | 2010-06-21 11:48:45 +0000 | [diff] [blame] | 242 | *ecn_ok = (options >> 5) & 1; |
Hannes Frederic Sowa | 5d134f1 | 2013-01-05 16:10:48 +0000 | [diff] [blame] | 243 | if (*ecn_ok && !net->ipv4.sysctl_tcp_ecn) |
Florian Westphal | 172d69e | 2010-06-21 11:48:45 +0000 | [diff] [blame] | 244 | return false; |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 245 | |
Florian Westphal | 8c76368 | 2010-06-16 14:42:15 -0700 | [diff] [blame] | 246 | if (tcp_opt->sack_ok && !sysctl_tcp_sack) |
| 247 | return false; |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 248 | |
Florian Westphal | 734f614 | 2010-06-21 11:48:44 +0000 | [diff] [blame] | 249 | if ((options & 0xf) == 0xf) |
| 250 | return true; /* no window scaling */ |
| 251 | |
| 252 | tcp_opt->wscale_ok = 1; |
| 253 | tcp_opt->snd_wscale = options & 0xf; |
| 254 | return sysctl_tcp_window_scaling != 0; |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 255 | } |
| 256 | EXPORT_SYMBOL(cookie_check_timestamp); |
| 257 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 258 | struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, |
| 259 | struct ip_options *opt) |
| 260 | { |
William Allen Simpson | 4957faade | 2009-12-02 18:25:27 +0000 | [diff] [blame] | 261 | struct tcp_options_received tcp_opt; |
Arnaldo Carvalho de Melo | 2e6599c | 2005-06-18 22:46:52 -0700 | [diff] [blame] | 262 | struct inet_request_sock *ireq; |
| 263 | struct tcp_request_sock *treq; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 264 | struct tcp_sock *tp = tcp_sk(sk); |
Arnaldo Carvalho de Melo | aa8223c | 2007-04-10 21:04:22 -0700 | [diff] [blame] | 265 | const struct tcphdr *th = tcp_hdr(skb); |
| 266 | __u32 cookie = ntohl(th->ack_seq) - 1; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 267 | struct sock *ret = sk; |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 268 | struct request_sock *req; |
| 269 | int mss; |
| 270 | struct rtable *rt; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 271 | __u8 rcv_wscale; |
Mike Waychison | f0e3d068 | 2011-08-10 21:59:57 -0700 | [diff] [blame] | 272 | bool ecn_ok = false; |
Eric Dumazet | dfd25ff | 2012-03-10 09:20:21 +0000 | [diff] [blame] | 273 | struct flowi4 fl4; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 274 | |
Florian Westphal | af9b473 | 2010-06-03 00:43:44 +0000 | [diff] [blame] | 275 | if (!sysctl_tcp_syncookies || !th->ack || th->rst) |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 276 | goto out; |
| 277 | |
Florian Westphal | a0f82f6 | 2009-04-19 09:43:48 +0000 | [diff] [blame] | 278 | if (tcp_synq_no_recent_overflow(sk) || |
Patrick McHardy | 0198230 | 2013-08-27 08:50:13 +0200 | [diff] [blame] | 279 | (mss = __cookie_v4_check(ip_hdr(skb), th, cookie)) == 0) { |
Pavel Emelyanov | de0744a | 2008-07-16 20:31:16 -0700 | [diff] [blame] | 280 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 281 | goto out; |
| 282 | } |
| 283 | |
Pavel Emelyanov | de0744a | 2008-07-16 20:31:16 -0700 | [diff] [blame] | 284 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV); |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 285 | |
David S. Miller | bb5b7c1 | 2009-12-15 20:56:42 -0800 | [diff] [blame] | 286 | /* check for timestamp cookie support */ |
| 287 | memset(&tcp_opt, 0, sizeof(tcp_opt)); |
Christoph Paasch | 1a2c618 | 2013-03-17 08:23:34 +0000 | [diff] [blame] | 288 | tcp_parse_options(skb, &tcp_opt, 0, NULL); |
David S. Miller | bb5b7c1 | 2009-12-15 20:56:42 -0800 | [diff] [blame] | 289 | |
Hannes Frederic Sowa | 5d134f1 | 2013-01-05 16:10:48 +0000 | [diff] [blame] | 290 | if (!cookie_check_timestamp(&tcp_opt, sock_net(sk), &ecn_ok)) |
Florian Westphal | 8c76368 | 2010-06-16 14:42:15 -0700 | [diff] [blame] | 291 | goto out; |
David S. Miller | bb5b7c1 | 2009-12-15 20:56:42 -0800 | [diff] [blame] | 292 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 293 | ret = NULL; |
Arnaldo Carvalho de Melo | ce4a7d0 | 2008-06-10 12:39:35 -0700 | [diff] [blame] | 294 | req = inet_reqsk_alloc(&tcp_request_sock_ops); /* for safety */ |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 295 | if (!req) |
| 296 | goto out; |
| 297 | |
Arnaldo Carvalho de Melo | 2e6599c | 2005-06-18 22:46:52 -0700 | [diff] [blame] | 298 | ireq = inet_rsk(req); |
| 299 | treq = tcp_rsk(req); |
Arnaldo Carvalho de Melo | aa8223c | 2007-04-10 21:04:22 -0700 | [diff] [blame] | 300 | treq->rcv_isn = ntohl(th->seq) - 1; |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 301 | treq->snt_isn = cookie; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 302 | req->mss = mss; |
Eric Dumazet | b44084c | 2013-10-10 00:04:37 -0700 | [diff] [blame] | 303 | ireq->ir_num = ntohs(th->dest); |
| 304 | ireq->ir_rmt_port = th->source; |
| 305 | ireq->ir_loc_addr = ip_hdr(skb)->daddr; |
| 306 | ireq->ir_rmt_addr = ip_hdr(skb)->saddr; |
Lorenzo Colitti | 84f39b0 | 2014-05-13 10:17:35 -0700 | [diff] [blame] | 307 | ireq->ir_mark = inet_request_mark(sk, skb); |
Florian Westphal | 172d69e | 2010-06-21 11:48:45 +0000 | [diff] [blame] | 308 | ireq->ecn_ok = ecn_ok; |
David S. Miller | bb5b7c1 | 2009-12-15 20:56:42 -0800 | [diff] [blame] | 309 | ireq->snd_wscale = tcp_opt.snd_wscale; |
David S. Miller | bb5b7c1 | 2009-12-15 20:56:42 -0800 | [diff] [blame] | 310 | ireq->sack_ok = tcp_opt.sack_ok; |
| 311 | ireq->wscale_ok = tcp_opt.wscale_ok; |
| 312 | ireq->tstamp_ok = tcp_opt.saw_tstamp; |
| 313 | req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0; |
Jerry Chu | 9ad7c04 | 2011-06-08 11:08:38 +0000 | [diff] [blame] | 314 | treq->snt_synack = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsecr : 0; |
Jerry Chu | 8336886 | 2012-08-31 12:29:12 +0000 | [diff] [blame] | 315 | treq->listener = NULL; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 316 | |
| 317 | /* We throwed the options of the initial SYN away, so we hope |
| 318 | * the ACK carries the same options again (see RFC1122 4.2.3.8) |
| 319 | */ |
| 320 | if (opt && opt->optlen) { |
Eric Dumazet | f6d8bd0 | 2011-04-21 09:45:37 +0000 | [diff] [blame] | 321 | int opt_size = sizeof(struct ip_options_rcu) + opt->optlen; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 322 | |
Arnaldo Carvalho de Melo | 2e6599c | 2005-06-18 22:46:52 -0700 | [diff] [blame] | 323 | ireq->opt = kmalloc(opt_size, GFP_ATOMIC); |
Eric Dumazet | f6d8bd0 | 2011-04-21 09:45:37 +0000 | [diff] [blame] | 324 | if (ireq->opt != NULL && ip_options_echo(&ireq->opt->opt, skb)) { |
Arnaldo Carvalho de Melo | 2e6599c | 2005-06-18 22:46:52 -0700 | [diff] [blame] | 325 | kfree(ireq->opt); |
| 326 | ireq->opt = NULL; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 327 | } |
| 328 | } |
| 329 | |
Paul Moore | 284904a | 2009-03-27 17:10:28 -0400 | [diff] [blame] | 330 | if (security_inet_conn_request(sk, skb, req)) { |
| 331 | reqsk_free(req); |
| 332 | goto out; |
| 333 | } |
| 334 | |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 335 | req->expires = 0UL; |
Eric Dumazet | e6c022a | 2012-10-27 23:16:46 +0000 | [diff] [blame] | 336 | req->num_retrans = 0; |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 337 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 338 | /* |
| 339 | * We need to lookup the route here to get at the correct |
| 340 | * window size. We should better make sure that the window size |
| 341 | * hasn't changed since we received the original syn, but I see |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 342 | * no easy way to do this. |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 343 | */ |
Lorenzo Colitti | 84f39b0 | 2014-05-13 10:17:35 -0700 | [diff] [blame] | 344 | flowi4_init_output(&fl4, sk->sk_bound_dev_if, ireq->ir_mark, |
Dmitry Popov | d66954a | 2013-04-11 08:55:07 +0000 | [diff] [blame] | 345 | RT_CONN_FLAGS(sk), RT_SCOPE_UNIVERSE, IPPROTO_TCP, |
Eric Dumazet | dfd25ff | 2012-03-10 09:20:21 +0000 | [diff] [blame] | 346 | inet_sk_flowi_flags(sk), |
Eric Dumazet | 634fb979 | 2013-10-09 15:21:29 -0700 | [diff] [blame] | 347 | (opt && opt->srr) ? opt->faddr : ireq->ir_rmt_addr, |
| 348 | ireq->ir_loc_addr, th->source, th->dest); |
Eric Dumazet | dfd25ff | 2012-03-10 09:20:21 +0000 | [diff] [blame] | 349 | security_req_classify_flow(req, flowi4_to_flowi(&fl4)); |
| 350 | rt = ip_route_output_key(sock_net(sk), &fl4); |
| 351 | if (IS_ERR(rt)) { |
| 352 | reqsk_free(req); |
| 353 | goto out; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 354 | } |
| 355 | |
| 356 | /* Try to redo what tcp_v4_send_synack did. */ |
Changli Gao | d8d1f30 | 2010-06-10 23:31:35 -0700 | [diff] [blame] | 357 | req->window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW); |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 358 | |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 359 | tcp_select_initial_window(tcp_full_space(sk), req->mss, |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 360 | &req->rcv_wnd, &req->window_clamp, |
laurent chavey | 31d1292 | 2009-12-15 11:15:28 +0000 | [diff] [blame] | 361 | ireq->wscale_ok, &rcv_wscale, |
Changli Gao | d8d1f30 | 2010-06-10 23:31:35 -0700 | [diff] [blame] | 362 | dst_metric(&rt->dst, RTAX_INITRWND)); |
Florian Westphal | 4dfc281 | 2008-04-10 03:12:40 -0700 | [diff] [blame] | 363 | |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 364 | ireq->rcv_wscale = rcv_wscale; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 365 | |
Changli Gao | d8d1f30 | 2010-06-10 23:31:35 -0700 | [diff] [blame] | 366 | ret = get_cookie_sock(sk, skb, req, &rt->dst); |
Eric Dumazet | dfd25ff | 2012-03-10 09:20:21 +0000 | [diff] [blame] | 367 | /* ip_queue_xmit() depends on our flow being setup |
| 368 | * Normal sockets get it right from inet_csk_route_child_sock() |
| 369 | */ |
| 370 | if (ret) |
| 371 | inet_sk(ret)->cork.fl.u.ip4 = fl4; |
Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 372 | out: return ret; |
| 373 | } |