* 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>
/*
* 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.
& 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,
int mssind;
const __u16 mss = *mssp;
-
+
tp->last_synq_overflow = jiffies;
/* XXX sort msstab[] by probability? Binary search? */
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 seq;
__u32 mssind;
- seq = ntohl(skb->h.th->seq)-1;
+ 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,
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;
+ __u32 cookie = ntohl(skb->h.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)
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 = ntohl(skb->h.th->seq) - 1;
- treq->snt_isn = cookie;
+ treq->snt_isn = cookie;
req->mss = mss;
- ireq->rmt_port = skb->h.th->source;
+ 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->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 =
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;
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