* 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.
+ * Missing: IPv6 support.
*/
#include <linux/tcp.h>
#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 u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
u32 count, int c)
{
__u32 tmp[16 + 5 + SHA_WORKSPACE_WORDS];
memcpy(tmp + 3, syncookie_secret[c], sizeof(syncookie_secret[c]));
- tmp[0] = saddr;
- tmp[1] = daddr;
- tmp[2] = (sport << 16) + dport;
+ 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,
+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;
/* XXX sort msstab[] by probability? Binary search? */
NET_INC_STATS_BH(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;
}
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 (time_after(jiffies, tp->last_synq_overflow + TCP_TIMEOUT_INIT) ||
(mss = cookie_check(skb, cookie)) == 0) {
- NET_INC_STATS_BH(LINUX_MIB_SYNCOOKIESFAILED);
+ NET_INC_STATS_BH(LINUX_MIB_SYNCOOKIESFAILED);
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->rmt_port = th->source;
+ ireq->loc_addr = ip_hdr(skb)->daddr;
+ ireq->rmt_addr = ip_hdr(skb)->saddr;
ireq->opt = NULL;
/* We throwed the options of the initial SYN away, so we hope
}
ireq->snd_wscale = ireq->rcv_wscale = ireq->tstamp_ok = 0;
- ireq->wscale_ok = ireq->sack_ok = 0;
- req->expires = 0UL;
- req->retrans = 0;
-
+ ireq->wscale_ok = ireq->sack_ok = 0;
+ 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 =
.tos = RT_CONN_FLAGS(sk) } },
.proto = IPPROTO_TCP,
.uli_u = { .ports =
- { .sport = skb->h.th->dest,
- .dport = skb->h.th->source } } };
+ { .sport = th->dest,
+ .dport = th->source } } };
security_req_classify_flow(req, &fl);
if (ip_route_output_key(&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);
tcp_select_initial_window(tcp_full_space(sk), req->mss,
- &req->rcv_wnd, &req->window_clamp,
+ &req->rcv_wnd, &req->window_clamp,
0, &rcv_wscale);
/* BTW win scale with syncookies is 0 by definition */
- ireq->rcv_wscale = rcv_wscale;
+ ireq->rcv_wscale = rcv_wscale;
ret = get_cookie_sock(sk, skb, req, &rt->u.dst);
out: return ret;