* Syncookies implementation for the Linux kernel
*
* Copyright (C) 1997 Andi Kleen
- * Based on ideas by D.J.Bernstein and Eric Schenk.
+ * Based on ideas by D.J.Bernstein and Eric Schenk.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
- *
- * $Id: syncookies.c,v 1.18 2002/02/01 22:01:04 davem Exp $
- *
- * Missing: IPv6 support.
*/
#include <linux/tcp.h>
#include <linux/cryptohash.h>
#include <linux/kernel.h>
#include <net/tcp.h>
+#include <net/route.h>
+
+/* Timestamps: lowest 9 bits store TCP options */
+#define TSBITS 9
+#define TSMASK (((__u32)1 << TSBITS) - 1)
extern int sysctl_tcp_syncookies;
-static __u32 syncookie_secret[2][16-3+SHA_DIGEST_WORDS];
+__u32 syncookie_secret[2][16-4+SHA_DIGEST_WORDS];
+EXPORT_SYMBOL(syncookie_secret);
static __init int init_syncookies(void)
{
get_random_bytes(syncookie_secret, sizeof(syncookie_secret));
return 0;
}
-module_init(init_syncookies);
+__initcall(init_syncookies);
#define COOKIEBITS 24 /* Upper bits store count */
#define COOKIEMASK (((__u32)1 << COOKIEBITS) - 1)
-static u32 cookie_hash(u32 saddr, u32 daddr, u32 sport, u32 dport,
+static DEFINE_PER_CPU(__u32 [16 + 5 + SHA_WORKSPACE_WORDS],
+ ipv4_cookie_scratch);
+
+static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
u32 count, int c)
{
- __u32 tmp[16 + 5 + SHA_WORKSPACE_WORDS];
+ __u32 *tmp = __get_cpu_var(ipv4_cookie_scratch);
- memcpy(tmp + 3, syncookie_secret[c], sizeof(syncookie_secret[c]));
- tmp[0] = saddr;
- tmp[1] = daddr;
- tmp[2] = (sport << 16) + dport;
+ memcpy(tmp + 4, syncookie_secret[c], sizeof(syncookie_secret[c]));
+ tmp[0] = (__force u32)saddr;
+ tmp[1] = (__force u32)daddr;
+ tmp[2] = ((__force u32)sport << 16) + (__force u32)dport;
tmp[3] = count;
sha_transform(tmp + 16, (__u8 *)tmp, tmp + 16 + 5);
return tmp[17];
}
-static __u32 secure_tcp_syn_cookie(__u32 saddr, __u32 daddr, __u16 sport,
- __u16 dport, __u32 sseq, __u32 count,
+
+/*
+ * when syncookies are in effect and tcp timestamps are enabled we encode
+ * tcp options in the lowest 9 bits of the timestamp value that will be
+ * sent in the syn-ack.
+ * Since subsequent timestamps use the normal tcp_time_stamp value, we
+ * must make sure that the resulting initial timestamp is <= tcp_time_stamp.
+ */
+__u32 cookie_init_timestamp(struct request_sock *req)
+{
+ struct inet_request_sock *ireq;
+ u32 ts, ts_now = tcp_time_stamp;
+ u32 options = 0;
+
+ ireq = inet_rsk(req);
+ if (ireq->wscale_ok) {
+ options = ireq->snd_wscale;
+ options |= ireq->rcv_wscale << 4;
+ }
+ options |= ireq->sack_ok << 8;
+
+ ts = ts_now & ~TSMASK;
+ ts |= options;
+ if (ts > ts_now) {
+ ts >>= TSBITS;
+ ts--;
+ ts <<= TSBITS;
+ ts |= options;
+ }
+ return ts;
+}
+
+
+static __u32 secure_tcp_syn_cookie(__be32 saddr, __be32 daddr, __be16 sport,
+ __be16 dport, __u32 sseq, __u32 count,
__u32 data)
{
/*
* Compute the secure sequence number.
* The output should be:
- * HASH(sec1,saddr,sport,daddr,dport,sec1) + sseq + (count * 2^24)
+ * HASH(sec1,saddr,sport,daddr,dport,sec1) + sseq + (count * 2^24)
* + (HASH(sec2,saddr,sport,daddr,dport,count,sec2) % 2^24).
* Where sseq is their sequence number and count increases every
* minute by 1.
* "maxdiff" if the current (passed-in) "count". The return value
* is (__u32)-1 if this test fails.
*/
-static __u32 check_tcp_syn_cookie(__u32 cookie, __u32 saddr, __u32 daddr,
- __u16 sport, __u16 dport, __u32 sseq,
+static __u32 check_tcp_syn_cookie(__u32 cookie, __be32 saddr, __be32 daddr,
+ __be16 sport, __be16 dport, __u32 sseq,
__u32 count, __u32 maxdiff)
{
__u32 diff;
& COOKIEMASK; /* Leaving the data behind */
}
-/*
+/*
* This table has to be sorted and terminated with (__u16)-1.
* XXX generate a better table.
* Unresolved Issues: HIPPI with a 64k MSS is not well supported.
*/
static __u16 const msstab[] = {
64 - 1,
- 256 - 1,
+ 256 - 1,
512 - 1,
536 - 1,
- 1024 - 1,
+ 1024 - 1,
1440 - 1,
1460 - 1,
4312 - 1,
*/
__u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, __u16 *mssp)
{
- struct tcp_sock *tp = tcp_sk(sk);
+ const struct iphdr *iph = ip_hdr(skb);
+ const struct tcphdr *th = tcp_hdr(skb);
int mssind;
const __u16 mss = *mssp;
-
- tp->last_synq_overflow = jiffies;
+ tcp_synq_overflow(sk);
/* XXX sort msstab[] by probability? Binary search? */
for (mssind = 0; mss > msstab[mssind + 1]; mssind++)
;
*mssp = msstab[mssind] + 1;
- NET_INC_STATS_BH(LINUX_MIB_SYNCOOKIESSENT);
+ NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
- return secure_tcp_syn_cookie(skb->nh.iph->saddr, skb->nh.iph->daddr,
- skb->h.th->source, skb->h.th->dest,
- ntohl(skb->h.th->seq),
+ return secure_tcp_syn_cookie(iph->saddr, iph->daddr,
+ th->source, th->dest, ntohl(th->seq),
jiffies / (HZ * 60), mssind);
}
-/*
+/*
* This (misnamed) value is the age of syncookie which is permitted.
* Its ideal value should be dependent on TCP_TIMEOUT_INIT and
* sysctl_tcp_retries1. It's a rather complicated formula (exponential
* backoff) to compute at runtime so it's currently hardcoded here.
*/
#define COUNTER_TRIES 4
-/*
- * Check if a ack sequence number is a valid syncookie.
+/*
+ * Check if a ack sequence number is a valid syncookie.
* Return the decoded mss if it is, or 0 if not.
*/
static inline int cookie_check(struct sk_buff *skb, __u32 cookie)
{
- __u32 seq;
- __u32 mssind;
-
- seq = ntohl(skb->h.th->seq)-1;
- mssind = check_tcp_syn_cookie(cookie,
- skb->nh.iph->saddr, skb->nh.iph->daddr,
- skb->h.th->source, skb->h.th->dest,
- seq, jiffies / (HZ * 60), COUNTER_TRIES);
+ const struct iphdr *iph = ip_hdr(skb);
+ const struct tcphdr *th = tcp_hdr(skb);
+ __u32 seq = ntohl(th->seq) - 1;
+ __u32 mssind = check_tcp_syn_cookie(cookie, iph->saddr, iph->daddr,
+ th->source, th->dest, seq,
+ jiffies / (HZ * 60),
+ COUNTER_TRIES);
return mssind < NUM_MSS ? msstab[mssind] + 1 : 0;
}
return child;
}
+
+/*
+ * when syncookies are in effect and tcp timestamps are enabled we stored
+ * additional tcp options in the timestamp.
+ * This extracts these options from the timestamp echo.
+ *
+ * The lowest 4 bits are for snd_wscale
+ * The next 4 lsb are for rcv_wscale
+ * The next lsb is for sack_ok
+ */
+void cookie_check_timestamp(struct tcp_options_received *tcp_opt)
+{
+ /* echoed timestamp, 9 lowest bits contain options */
+ u32 options = tcp_opt->rcv_tsecr & TSMASK;
+
+ tcp_opt->snd_wscale = options & 0xf;
+ options >>= 4;
+ tcp_opt->rcv_wscale = options & 0xf;
+
+ tcp_opt->sack_ok = (options >> 4) & 0x1;
+
+ if (tcp_opt->sack_ok)
+ tcp_sack_reset(tcp_opt);
+
+ if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale)
+ tcp_opt->wscale_ok = 1;
+}
+EXPORT_SYMBOL(cookie_check_timestamp);
+
struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
struct ip_options *opt)
{
+ struct tcp_options_received tcp_opt;
+ u8 *hash_location;
struct inet_request_sock *ireq;
struct tcp_request_sock *treq;
struct tcp_sock *tp = tcp_sk(sk);
- __u32 cookie = ntohl(skb->h.th->ack_seq) - 1;
+ const struct tcphdr *th = tcp_hdr(skb);
+ __u32 cookie = ntohl(th->ack_seq) - 1;
struct sock *ret = sk;
- struct request_sock *req;
- int mss;
- struct rtable *rt;
+ struct request_sock *req;
+ int mss;
+ struct rtable *rt;
__u8 rcv_wscale;
- if (!sysctl_tcp_syncookies || !skb->h.th->ack)
+ if (!sysctl_tcp_syncookies || !th->ack)
goto out;
- if (time_after(jiffies, tp->last_synq_overflow + TCP_TIMEOUT_INIT) ||
+ if (tcp_synq_no_recent_overflow(sk) ||
(mss = cookie_check(skb, cookie)) == 0) {
- NET_INC_STATS_BH(LINUX_MIB_SYNCOOKIESFAILED);
+ NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESFAILED);
goto out;
}
- NET_INC_STATS_BH(LINUX_MIB_SYNCOOKIESRECV);
+ NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESRECV);
+
+ /* check for timestamp cookie support */
+ memset(&tcp_opt, 0, sizeof(tcp_opt));
+ tcp_parse_options(skb, &tcp_opt, &hash_location, 0);
+
+ if (tcp_opt.saw_tstamp)
+ cookie_check_timestamp(&tcp_opt);
ret = NULL;
- req = reqsk_alloc(&tcp_request_sock_ops); /* for safety */
+ req = inet_reqsk_alloc(&tcp_request_sock_ops); /* for safety */
if (!req)
goto out;
ireq = inet_rsk(req);
treq = tcp_rsk(req);
- treq->rcv_isn = htonl(skb->h.th->seq) - 1;
- treq->snt_isn = cookie;
+ treq->rcv_isn = ntohl(th->seq) - 1;
+ treq->snt_isn = cookie;
req->mss = mss;
- ireq->rmt_port = skb->h.th->source;
- ireq->loc_addr = skb->nh.iph->daddr;
- ireq->rmt_addr = skb->nh.iph->saddr;
- ireq->opt = NULL;
+ ireq->loc_port = th->dest;
+ ireq->rmt_port = th->source;
+ ireq->loc_addr = ip_hdr(skb)->daddr;
+ ireq->rmt_addr = ip_hdr(skb)->saddr;
+ ireq->ecn_ok = 0;
+ ireq->snd_wscale = tcp_opt.snd_wscale;
+ ireq->rcv_wscale = tcp_opt.rcv_wscale;
+ ireq->sack_ok = tcp_opt.sack_ok;
+ ireq->wscale_ok = tcp_opt.wscale_ok;
+ ireq->tstamp_ok = tcp_opt.saw_tstamp;
+ req->ts_recent = tcp_opt.saw_tstamp ? tcp_opt.rcv_tsval : 0;
/* We throwed the options of the initial SYN away, so we hope
* the ACK carries the same options again (see RFC1122 4.2.3.8)
}
}
- ireq->snd_wscale = ireq->rcv_wscale = ireq->tstamp_ok = 0;
- ireq->wscale_ok = ireq->sack_ok = 0;
- req->expires = 0UL;
- req->retrans = 0;
-
+ if (security_inet_conn_request(sk, skb, req)) {
+ reqsk_free(req);
+ goto out;
+ }
+
+ req->expires = 0UL;
+ req->retrans = 0;
+
/*
* We need to lookup the route here to get at the correct
* window size. We should better make sure that the window size
* hasn't changed since we received the original syn, but I see
- * no easy way to do this.
+ * no easy way to do this.
*/
{
- struct flowi fl = { .nl_u = { .ip4_u =
+ struct flowi fl = { .mark = sk->sk_mark,
+ .nl_u = { .ip4_u =
{ .daddr = ((opt && opt->srr) ?
opt->faddr :
ireq->rmt_addr),
.saddr = ireq->loc_addr,
.tos = RT_CONN_FLAGS(sk) } },
.proto = IPPROTO_TCP,
+ .flags = inet_sk_flowi_flags(sk),
.uli_u = { .ports =
- { .sport = skb->h.th->dest,
- .dport = skb->h.th->source } } };
- if (ip_route_output_key(&rt, &fl)) {
+ { .sport = th->dest,
+ .dport = th->source } } };
+ security_req_classify_flow(req, &fl);
+ if (ip_route_output_key(&init_net, &rt, &fl)) {
reqsk_free(req);
- goto out;
+ goto out;
}
}
/* Try to redo what tcp_v4_send_synack did. */
- req->window_clamp = dst_metric(&rt->u.dst, RTAX_WINDOW);
+ req->window_clamp = tp->window_clamp ? :dst_metric(&rt->u.dst, RTAX_WINDOW);
+
tcp_select_initial_window(tcp_full_space(sk), req->mss,
- &req->rcv_wnd, &req->window_clamp,
- 0, &rcv_wscale);
- /* BTW win scale with syncookies is 0 by definition */
- ireq->rcv_wscale = rcv_wscale;
+ &req->rcv_wnd, &req->window_clamp,
+ ireq->wscale_ok, &rcv_wscale);
+
+ ireq->rcv_wscale = rcv_wscale;
ret = get_cookie_sock(sk, skb, req, &rt->u.dst);
out: return ret;
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff