diff options
Diffstat (limited to 'pfinet/linux-src/net/ipv4/syncookies.c')
| -rw-r--r-- | pfinet/linux-src/net/ipv4/syncookies.c | 201 |
1 files changed, 201 insertions, 0 deletions
diff --git a/pfinet/linux-src/net/ipv4/syncookies.c b/pfinet/linux-src/net/ipv4/syncookies.c new file mode 100644 index 00000000..fb4e8f80 --- /dev/null +++ b/pfinet/linux-src/net/ipv4/syncookies.c @@ -0,0 +1,201 @@ +/* + * Syncookies implementation for the Linux kernel + * + * Copyright (C) 1997 Andi Kleen + * 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 1.7.2.1 1999/08/08 08:43:13 davem Exp $ + * + * Missing: IPv6 support. + */ + +#include <linux/config.h> +#if defined(CONFIG_SYN_COOKIES) +#include <linux/tcp.h> +#include <linux/malloc.h> +#include <linux/random.h> +#include <net/tcp.h> + +extern int sysctl_tcp_syncookies; + +static unsigned long tcp_lastsynq_overflow; + +/* + * 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, + 512-1, + 536-1, + 1024-1, + 1440-1, + 1460-1, + 4312-1, + (__u16)-1 +}; +/* The number doesn't include the -1 terminator */ +#define NUM_MSS (sizeof(msstab)/sizeof(msstab[0]) - 1) + +/* + * Generate a syncookie. mssp points to the mss, which is returned + * rounded down to the value encoded in the cookie. + */ +__u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb, + __u16 *mssp) +{ + int mssind; + const __u16 mss = *mssp; + + tcp_lastsynq_overflow = jiffies; + /* XXX sort msstab[] by probability? Binary search? */ + for (mssind = 0; mss > msstab[mssind+1]; mssind++) + ; + *mssp = msstab[mssind]+1; + + net_statistics.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), + 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. + * 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; + + if ((jiffies - tcp_lastsynq_overflow) > TCP_TIMEOUT_INIT) + return 0; + + 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); + + return mssind < NUM_MSS ? msstab[mssind]+1 : 0; +} + +extern struct or_calltable or_ipv4; + +static inline struct sock * +get_cookie_sock(struct sock *sk, struct sk_buff *skb, struct open_request *req, + struct dst_entry *dst) +{ + struct tcp_opt *tp = &sk->tp_pinfo.af_tcp; + + sk = tp->af_specific->syn_recv_sock(sk, skb, req, dst); + req->sk = sk; + + /* Queue up for accept() */ + tcp_synq_queue(tp, req); + + return sk; +} + +struct sock * +cookie_v4_check(struct sock *sk, struct sk_buff *skb, struct ip_options *opt) +{ + __u32 cookie = ntohl(skb->h.th->ack_seq)-1; + struct open_request *req; + int mss; + struct rtable *rt; + __u8 rcv_wscale; + + if (!sysctl_tcp_syncookies) + return sk; + if (!skb->h.th->ack) + return sk; + + mss = cookie_check(skb, cookie); + if (mss == 0) { + net_statistics.SyncookiesFailed++; + return sk; + } + + net_statistics.SyncookiesRecv++; + + req = tcp_openreq_alloc(); + if (req == NULL) + return NULL; + + req->rcv_isn = htonl(skb->h.th->seq)-1; + req->snt_isn = cookie; + req->mss = mss; + req->rmt_port = skb->h.th->source; + req->af.v4_req.loc_addr = skb->nh.iph->daddr; + req->af.v4_req.rmt_addr = skb->nh.iph->saddr; + req->class = &or_ipv4; /* for safety */ +#ifdef CONFIG_IP_TRANSPARENT_PROXY + req->lcl_port = skb->h.th->dest; +#endif + + req->af.v4_req.opt = NULL; + + /* 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) + */ + if (opt && opt->optlen) { + int opt_size = sizeof(struct ip_options) + opt->optlen; + + req->af.v4_req.opt = kmalloc(opt_size, GFP_ATOMIC); + if (req->af.v4_req.opt) { + if (ip_options_echo(req->af.v4_req.opt, skb)) { + kfree_s(req->af.v4_req.opt, opt_size); + req->af.v4_req.opt = NULL; + } + } + } + + req->snd_wscale = req->rcv_wscale = req->tstamp_ok = 0; + req->wscale_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. + */ + if (ip_route_output(&rt, + opt && + opt->srr ? opt->faddr : req->af.v4_req.rmt_addr, + req->af.v4_req.loc_addr, + sk->ip_tos | RTO_CONN, + 0)) { + tcp_openreq_free(req); + return NULL; + } + + /* Try to redo what tcp_v4_send_synack did. */ + req->window_clamp = rt->u.dst.window; + tcp_select_initial_window(sock_rspace(sk)/2,req->mss, + &req->rcv_wnd, &req->window_clamp, + 0, &rcv_wscale); + req->rcv_wscale = rcv_wscale; + + return get_cookie_sock(sk, skb, req, &rt->u.dst); +} + +#endif |