#include <net/tcp.h>
#include <net/route.h>
-/* Timestamps: lowest 9 bits store TCP options */
-#define TSBITS 9
+/* Timestamps: lowest bits store TCP options */
+#define TSBITS 6
#define TSMASK (((__u32)1 << TSBITS) - 1)
extern int sysctl_tcp_syncookies;
/*
* 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
+ * tcp options in the lower 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 options = 0;
ireq = inet_rsk(req);
- if (ireq->wscale_ok) {
- options = ireq->snd_wscale;
- options |= ireq->rcv_wscale << 4;
- }
- options |= ireq->sack_ok << 8;
+
+ options = ireq->wscale_ok ? ireq->snd_wscale : 0xf;
+ options |= ireq->sack_ok << 4;
+ options |= ireq->ecn_ok << 5;
ts = ts_now & ~TSMASK;
ts |= options;
}
/*
- * 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.
+ * MSS Values are taken from the 2009 paper
+ * 'Measuring TCP Maximum Segment Size' by S. Alcock and R. Nelson:
+ * - values 1440 to 1460 accounted for 80% of observed mss values
+ * - values outside the 536-1460 range are rare (<0.2%).
+ *
+ * Table must be sorted.
*/
static __u16 const msstab[] = {
- 64 - 1,
- 256 - 1,
- 512 - 1,
- 536 - 1,
- 1024 - 1,
- 1440 - 1,
- 1460 - 1,
- 4312 - 1,
- (__u16)-1
+ 64,
+ 512,
+ 536,
+ 1024,
+ 1440,
+ 1460,
+ 4312,
+ 8960,
};
-/* The number doesn't include the -1 terminator */
-#define NUM_MSS (ARRAY_SIZE(msstab) - 1)
/*
* Generate a syncookie. mssp points to the mss, which is returned
tcp_synq_overflow(sk);
- /* XXX sort msstab[] by probability? Binary search? */
- for (mssind = 0; mss > msstab[mssind + 1]; mssind++)
- ;
- *mssp = msstab[mssind] + 1;
+ for (mssind = ARRAY_SIZE(msstab) - 1; mssind ; mssind--)
+ if (mss >= msstab[mssind])
+ break;
+ *mssp = msstab[mssind];
NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SYNCOOKIESSENT);
jiffies / (HZ * 60),
COUNTER_TRIES);
- return mssind < NUM_MSS ? msstab[mssind] + 1 : 0;
+ return mssind < ARRAY_SIZE(msstab) ? msstab[mssind] : 0;
}
static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
* 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
+ * The lowest 4 bits store snd_wscale.
+ * next 2 bits indicate SACK and ECN support.
+ *
+ * return false if we decode an option that should not be.
*/
-void cookie_check_timestamp(struct tcp_options_received *tcp_opt)
+bool cookie_check_timestamp(struct tcp_options_received *tcp_opt, bool *ecn_ok)
{
- /* echoed timestamp, 9 lowest bits contain options */
+ /* echoed timestamp, 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;
+ if (!tcp_opt->saw_tstamp) {
+ tcp_clear_options(tcp_opt);
+ return true;
+ }
+
+ if (!sysctl_tcp_timestamps)
+ return false;
tcp_opt->sack_ok = (options >> 4) & 0x1;
+ *ecn_ok = (options >> 5) & 1;
+ if (*ecn_ok && !sysctl_tcp_ecn)
+ return false;
+
+ if (tcp_opt->sack_ok && !sysctl_tcp_sack)
+ return false;
- if (tcp_opt->sack_ok)
- tcp_sack_reset(tcp_opt);
+ if ((options & 0xf) == 0xf)
+ return true; /* no window scaling */
- if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale)
- tcp_opt->wscale_ok = 1;
+ tcp_opt->wscale_ok = 1;
+ tcp_opt->snd_wscale = options & 0xf;
+ return sysctl_tcp_window_scaling != 0;
}
EXPORT_SYMBOL(cookie_check_timestamp);
int mss;
struct rtable *rt;
__u8 rcv_wscale;
+ bool ecn_ok;
- if (!sysctl_tcp_syncookies || !th->ack)
+ if (!sysctl_tcp_syncookies || !th->ack || th->rst)
goto out;
if (tcp_synq_no_recent_overflow(sk) ||
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);
+ if (!cookie_check_timestamp(&tcp_opt, &ecn_ok))
+ goto out;
ret = NULL;
req = inet_reqsk_alloc(&tcp_request_sock_ops); /* for safety */
ireq->rmt_port = th->source;
ireq->loc_addr = ip_hdr(skb)->daddr;
ireq->rmt_addr = ip_hdr(skb)->saddr;
- ireq->ecn_ok = 0;
+ ireq->ecn_ok = ecn_ok;
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;
*/
{
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) } },
+ .fl4_dst = ((opt && opt->srr) ?
+ opt->faddr : ireq->rmt_addr),
+ .fl4_src = ireq->loc_addr,
+ .fl4_tos = RT_CONN_FLAGS(sk),
.proto = IPPROTO_TCP,
.flags = inet_sk_flowi_flags(sk),
- .uli_u = { .ports =
- { .sport = th->dest,
- .dport = th->source } } };
+ .fl_ip_sport = th->dest,
+ .fl_ip_dport = th->source };
security_req_classify_flow(req, &fl);
if (ip_route_output_key(sock_net(sk), &rt, &fl)) {
reqsk_free(req);
}
/* Try to redo what tcp_v4_send_synack did. */
- req->window_clamp = tp->window_clamp ? :dst_metric(&rt->u.dst, RTAX_WINDOW);
+ req->window_clamp = tp->window_clamp ? :dst_metric(&rt->dst, RTAX_WINDOW);
tcp_select_initial_window(tcp_full_space(sk), req->mss,
&req->rcv_wnd, &req->window_clamp,
ireq->wscale_ok, &rcv_wscale,
- dst_metric(&rt->u.dst, RTAX_INITRWND));
+ dst_metric(&rt->dst, RTAX_INITRWND));
ireq->rcv_wscale = rcv_wscale;
- ret = get_cookie_sock(sk, skb, req, &rt->u.dst);
+ ret = get_cookie_sock(sk, skb, req, &rt->dst);
out: return ret;
}
git://bbs.cooldavid.org / net-next-2.6.git / blobdiff