![David S. Miller](/assets/img/avatar_default.png)
It creates a regression, triggering badness for SYN_RECV sockets, for example: [19148.022102] Badness at net/ipv4/inet_connection_sock.c:293 [19148.022570] NIP: c02a0914 LR: c02a0904 CTR: 00000000 [19148.023035] REGS: eeecbd30 TRAP: 0700 Not tainted (2.6.32) [19148.023496] MSR: 00029032 <EE,ME,CE,IR,DR> CR: 24002442 XER: 00000000 [19148.024012] TASK = eee9a820[1756] 'privoxy' THREAD: eeeca000 This is likely caused by the change in the 'estab' parameter passed to tcp_parse_options() when invoked by the functions in net/ipv4/tcp_minisocks.c But even if that is fixed, the ->conn_request() changes made in this patch series is fundamentally wrong. They try to use the listening socket's 'dst' to probe the route settings. The listening socket doesn't even have a route, and you can't get the right route (the child request one) until much later after we setup all of the state, and it must be done by hand. This stuff really isn't ready, so the best thing to do is a full revert. This reverts the following commits:f55017a93f
022c3f7d82
1aba721eba
cda42ebd67
345cda2fd6
dc343475ed
05eaade278
6a2a2d6bf8
Signed-off-by: David S. Miller <davem@davemloft.net>
368 lines
10 KiB
C
368 lines
10 KiB
C
/*
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* Syncookies implementation for the Linux kernel
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*
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* Copyright (C) 1997 Andi Kleen
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* Based on ideas by D.J.Bernstein and Eric Schenk.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/tcp.h>
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#include <linux/slab.h>
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#include <linux/random.h>
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#include <linux/cryptohash.h>
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#include <linux/kernel.h>
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#include <net/tcp.h>
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#include <net/route.h>
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/* Timestamps: lowest 9 bits store TCP options */
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#define TSBITS 9
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#define TSMASK (((__u32)1 << TSBITS) - 1)
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extern int sysctl_tcp_syncookies;
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__u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
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EXPORT_SYMBOL(syncookie_secret);
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static __init int init_syncookies(void)
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{
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get_random_bytes(syncookie_secret, sizeof(syncookie_secret));
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return 0;
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}
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__initcall(init_syncookies);
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#define COOKIEBITS 24 /* Upper bits store count */
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#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
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static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
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ipv4_cookie_scratch);
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static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
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u32 count, int c)
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{
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__u32 *tmp = __get_cpu_var(ipv4_cookie_scratch);
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memcpy(tmp + 4, syncookie_secret[c], sizeof(syncookie_secret[c]));
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tmp[0] = (__force u32)saddr;
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tmp[1] = (__force u32)daddr;
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tmp[2] = ((__force u32)sport << 16) + (__force u32)dport;
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tmp[3] = count;
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sha_transform(tmp + 16, (__u8 *)tmp, tmp + 16 + 5);
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return tmp[17];
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}
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/*
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* when syncookies are in effect and tcp timestamps are enabled we encode
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* tcp options in the lowest 9 bits of the timestamp value that will be
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* sent in the syn-ack.
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* Since subsequent timestamps use the normal tcp_time_stamp value, we
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* must make sure that the resulting initial timestamp is <= tcp_time_stamp.
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*/
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__u32 cookie_init_timestamp(struct request_sock *req)
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{
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struct inet_request_sock *ireq;
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u32 ts, ts_now = tcp_time_stamp;
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u32 options = 0;
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ireq = inet_rsk(req);
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if (ireq->wscale_ok) {
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options = ireq->snd_wscale;
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options |= ireq->rcv_wscale << 4;
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}
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options |= ireq->sack_ok << 8;
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ts = ts_now & ~TSMASK;
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ts |= options;
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if (ts > ts_now) {
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ts >>= TSBITS;
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ts--;
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ts <<= TSBITS;
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ts |= options;
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}
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return ts;
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}
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static __u32 secure_tcp_syn_cookie(__be32 saddr, __be32 daddr, __be16 sport,
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__be16 dport, __u32 sseq, __u32 count,
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__u32 data)
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{
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/*
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* Compute the secure sequence number.
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* The output should be:
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* HASH(sec1,saddr,sport,daddr,dport,sec1) + sseq + (count * 2^24)
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* + (HASH(sec2,saddr,sport,daddr,dport,count,sec2) % 2^24).
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* Where sseq is their sequence number and count increases every
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* minute by 1.
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* As an extra hack, we add a small "data" value that encodes the
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* MSS into the second hash value.
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*/
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return (cookie_hash(saddr, daddr, sport, dport, 0, 0) +
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sseq + (count << COOKIEBITS) +
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((cookie_hash(saddr, daddr, sport, dport, count, 1) + data)
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& COOKIEMASK));
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}
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/*
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* This retrieves the small "data" value from the syncookie.
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* If the syncookie is bad, the data returned will be out of
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* range. This must be checked by the caller.
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*
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* The count value used to generate the cookie must be within
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* "maxdiff" if the current (passed-in) "count". The return value
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* is (__u32)-1 if this test fails.
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*/
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static __u32 check_tcp_syn_cookie(__u32 cookie, __be32 saddr, __be32 daddr,
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__be16 sport, __be16 dport, __u32 sseq,
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__u32 count, __u32 maxdiff)
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{
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__u32 diff;
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/* Strip away the layers from the cookie */
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cookie -= cookie_hash(saddr, daddr, sport, dport, 0, 0) + sseq;
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/* Cookie is now reduced to (count * 2^24) ^ (hash % 2^24) */
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diff = (count - (cookie >> COOKIEBITS)) & ((__u32) - 1 >> COOKIEBITS);
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if (diff >= maxdiff)
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return (__u32)-1;
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return (cookie -
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cookie_hash(saddr, daddr, sport, dport, count - diff, 1))
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& COOKIEMASK; /* Leaving the data behind */
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}
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/*
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* This table has to be sorted and terminated with (__u16)-1.
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* XXX generate a better table.
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* Unresolved Issues: HIPPI with a 64k MSS is not well supported.
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*/
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static __u16 const msstab[] = {
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64 - 1,
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256 - 1,
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512 - 1,
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536 - 1,
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1024 - 1,
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1440 - 1,
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1460 - 1,
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4312 - 1,
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(__u16)-1
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};
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/* The number doesn't include the -1 terminator */
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#define NUM_MSS (ARRAY_SIZE(msstab) - 1)
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/*
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* Generate a syncookie. mssp points to the mss, which is returned
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* rounded down to the value encoded in the cookie.
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*/
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__u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
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{
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const struct iphdr *iph = ip_hdr(skb);
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const struct tcphdr *th = tcp_hdr(skb);
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int mssind;
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const __u16 mss = *mssp;
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tcp_synq_overflow(sk);
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/* XXX sort msstab[] by probability? Binary search? */
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for (mssind = 0; mss > msstab[mssind + 1]; mssind++)
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;
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*mssp = msstab[mssind] + 1;
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
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return secure_tcp_syn_cookie(iph->saddr, iph->daddr,
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th->source, th->dest, ntohl(th->seq),
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jiffies / (HZ * 60), mssind);
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}
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/*
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* This (misnamed) value is the age of syncookie which is permitted.
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* Its ideal value should be dependent on TCP_TIMEOUT_INIT and
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* sysctl_tcp_retries1. It's a rather complicated formula (exponential
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* backoff) to compute at runtime so it's currently hardcoded here.
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*/
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#define COUNTER_TRIES 4
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/*
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* Check if a ack sequence number is a valid syncookie.
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* Return the decoded mss if it is, or 0 if not.
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*/
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static inline int cookie_check(struct sk_buff *skb, __u32 cookie)
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{
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const struct iphdr *iph = ip_hdr(skb);
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const struct tcphdr *th = tcp_hdr(skb);
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__u32 seq = ntohl(th->seq) - 1;
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__u32 mssind = check_tcp_syn_cookie(cookie, iph->saddr, iph->daddr,
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th->source, th->dest, seq,
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jiffies / (HZ * 60),
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COUNTER_TRIES);
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return mssind < NUM_MSS ? msstab[mssind] + 1 : 0;
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}
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static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
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struct request_sock *req,
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struct dst_entry *dst)
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{
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struct inet_connection_sock *icsk = inet_csk(sk);
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struct sock *child;
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child = icsk->icsk_af_ops->syn_recv_sock(sk, skb, req, dst);
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if (child)
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inet_csk_reqsk_queue_add(sk, req, child);
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else
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reqsk_free(req);
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return child;
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}
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/*
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* when syncookies are in effect and tcp timestamps are enabled we stored
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* additional tcp options in the timestamp.
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* This extracts these options from the timestamp echo.
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*
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* The lowest 4 bits are for snd_wscale
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* The next 4 lsb are for rcv_wscale
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* The next lsb is for sack_ok
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*/
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void cookie_check_timestamp(struct tcp_options_received *tcp_opt)
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{
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/* echoed timestamp, 9 lowest bits contain options */
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u32 options = tcp_opt->rcv_tsecr & TSMASK;
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tcp_opt->snd_wscale = options & 0xf;
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options >>= 4;
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tcp_opt->rcv_wscale = options & 0xf;
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tcp_opt->sack_ok = (options >> 4) & 0x1;
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if (tcp_opt->sack_ok)
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tcp_sack_reset(tcp_opt);
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if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale)
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tcp_opt->wscale_ok = 1;
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}
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EXPORT_SYMBOL(cookie_check_timestamp);
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struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
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struct ip_options *opt)
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{
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struct tcp_options_received tcp_opt;
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u8 *hash_location;
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struct inet_request_sock *ireq;
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struct tcp_request_sock *treq;
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struct tcp_sock *tp = tcp_sk(sk);
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const struct tcphdr *th = tcp_hdr(skb);
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__u32 cookie = ntohl(th->ack_seq) - 1;
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struct sock *ret = sk;
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struct request_sock *req;
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int mss;
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struct rtable *rt;
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__u8 rcv_wscale;
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if (!sysctl_tcp_syncookies || !th->ack)
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goto out;
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if (tcp_synq_no_recent_overflow(sk) ||
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(mss = cookie_check(skb, cookie)) == 0) {
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
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goto out;
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}
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NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
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/* check for timestamp cookie support */
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memset(&tcp_opt, 0, sizeof(tcp_opt));
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tcp_parse_options(skb, &tcp_opt, &hash_location, 0);
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if (tcp_opt.saw_tstamp)
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cookie_check_timestamp(&tcp_opt);
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ret = NULL;
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req = inet_reqsk_alloc(&tcp_request_sock_ops); /* for safety */
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if (!req)
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goto out;
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ireq = inet_rsk(req);
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treq = tcp_rsk(req);
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treq->rcv_isn = ntohl(th->seq) - 1;
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treq->snt_isn = cookie;
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req->mss = mss;
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ireq->loc_port = th->dest;
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ireq->rmt_port = th->source;
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ireq->loc_addr = ip_hdr(skb)->daddr;
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ireq->rmt_addr = ip_hdr(skb)->saddr;
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ireq->ecn_ok = 0;
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ireq->snd_wscale = tcp_opt.snd_wscale;
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ireq->rcv_wscale = tcp_opt.rcv_wscale;
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ireq->sack_ok = tcp_opt.sack_ok;
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ireq->wscale_ok = tcp_opt.wscale_ok;
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ireq->tstamp_ok = tcp_opt.saw_tstamp;
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req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
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/* We throwed the options of the initial SYN away, so we hope
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* the ACK carries the same options again (see RFC1122 4.2.3.8)
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*/
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if (opt && opt->optlen) {
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int opt_size = sizeof(struct ip_options) + opt->optlen;
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ireq->opt = kmalloc(opt_size, GFP_ATOMIC);
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if (ireq->opt != NULL && ip_options_echo(ireq->opt, skb)) {
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kfree(ireq->opt);
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ireq->opt = NULL;
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}
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}
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if (security_inet_conn_request(sk, skb, req)) {
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reqsk_free(req);
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goto out;
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}
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req->expires = 0UL;
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req->retrans = 0;
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/*
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* We need to lookup the route here to get at the correct
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* window size. We should better make sure that the window size
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* hasn't changed since we received the original syn, but I see
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* no easy way to do this.
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*/
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{
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struct flowi fl = { .mark = sk->sk_mark,
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.nl_u = { .ip4_u =
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{ .daddr = ((opt && opt->srr) ?
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opt->faddr :
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ireq->rmt_addr),
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.saddr = ireq->loc_addr,
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.tos = RT_CONN_FLAGS(sk) } },
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.proto = IPPROTO_TCP,
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.flags = inet_sk_flowi_flags(sk),
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.uli_u = { .ports =
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{ .sport = th->dest,
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.dport = th->source } } };
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security_req_classify_flow(req, &fl);
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if (ip_route_output_key(&init_net, &rt, &fl)) {
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reqsk_free(req);
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goto out;
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}
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}
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/* Try to redo what tcp_v4_send_synack did. */
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req->window_clamp = tp->window_clamp ? :dst_metric(&rt->u.dst, RTAX_WINDOW);
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tcp_select_initial_window(tcp_full_space(sk), req->mss,
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&req->rcv_wnd, &req->window_clamp,
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ireq->wscale_ok, &rcv_wscale);
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ireq->rcv_wscale = rcv_wscale;
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ret = get_cookie_sock(sk, skb, req, &rt->u.dst);
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out: return ret;
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}
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