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syncookies: add support for ECN

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Allows use of ECN when syncookies are in effect by encoding ecn_ok
into the syn-ack tcp timestamp.

While at it, remove a uneeded #ifdef CONFIG_SYN_COOKIES.
With CONFIG_SYN_COOKIES=nm want_cookie is ifdef'd to 0 and gcc
removes the "if (0)".

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal
2010-06-21 11:48:45 +00:00
committed by David S. Miller
parent 734f614bc1
commit 172d69e63c
5 changed files with 17 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
net/ipv4/syncookies.c
View File

@@ -19,7 +19,7 @@
#include <net/route.h>
/* Timestamps: lowest bits store TCP options */
#define TSBITS 5
#define TSBITS 6
#define TSMASK (((__u32)1 << TSBITS) - 1)
extern int sysctl_tcp_syncookies;
@@ -73,6 +73,7 @@ __u32 cookie_init_timestamp(struct request_sock *req)
options = ireq->wscale_ok ? ireq->snd_wscale : 0xf;
options |= ireq->sack_ok << 4;
options |= ireq->ecn_ok << 5;
ts = ts_now & ~TSMASK;
ts |= options;
@@ -226,11 +227,11 @@ static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
* This extracts these options from the timestamp echo.
*
* The lowest 4 bits store snd_wscale.
* The next lsb is for sack_ok
* next 2 bits indicate SACK and ECN support.
*
* return false if we decode an option that should not be.
*/
bool cookie_check_timestamp(struct tcp_options_received *tcp_opt)
bool cookie_check_timestamp(struct tcp_options_received *tcp_opt, bool *ecn_ok)
{
/* echoed timestamp, lowest bits contain options */
u32 options = tcp_opt->rcv_tsecr & TSMASK;
@@ -244,6 +245,9 @@ bool cookie_check_timestamp(struct tcp_options_received *tcp_opt)
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;
@@ -272,6 +276,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
int mss;
struct rtable *rt;
__u8 rcv_wscale;
bool ecn_ok;
if (!sysctl_tcp_syncookies || !th->ack || th->rst)
goto out;
@@ -288,7 +293,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
memset(&tcp_opt, 0, sizeof(tcp_opt));
tcp_parse_options(skb, &tcp_opt, &hash_location, 0);
if (!cookie_check_timestamp(&tcp_opt))
if (!cookie_check_timestamp(&tcp_opt, &ecn_ok))
goto out;
ret = NULL;
@@ -305,7 +310,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
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->sack_ok = tcp_opt.sack_ok;
ireq->wscale_ok = tcp_opt.wscale_ok;