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Message-Id: <1276464875-4460-1-git-send-email-fw@strlen.de>
Date: Sun, 13 Jun 2010 23:34:35 +0200
From: Florian Westphal <fw@...len.de>
To: <netdev@...r.kernel.org>
Cc: Florian Westphal <fw@...len.de>
Subject: [PATCH net-next-2.6] syncookies: check decoded options against sysctl settings
Discard the ACK if we find options that do not match current sysctl
settings.
Previously it was possible to create a connection with sack,
wscale, etc. enabled even if the feature was disabled via sysctl.
Signed-off-by: Florian Westphal <fw@...len.de>
---
include/net/tcp.h | 2 +-
net/ipv4/syncookies.c | 25 +++++++++++++++++++------
net/ipv6/syncookies.c | 4 ++--
3 files changed, 22 insertions(+), 9 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 5731664..cca040e 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -464,7 +464,7 @@ extern __u32 cookie_v4_init_sequence(struct sock *sk, struct sk_buff *skb,
__u16 *mss);
extern __u32 cookie_init_timestamp(struct request_sock *req);
-extern void cookie_check_timestamp(struct tcp_options_received *tcp_opt);
+extern bool cookie_check_timestamp(struct tcp_options_received *tcp_opt);
/* From net/ipv6/syncookies.c */
extern struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c
index 02bef6a..51b5662 100644
--- a/net/ipv4/syncookies.c
+++ b/net/ipv4/syncookies.c
@@ -230,23 +230,36 @@ static inline struct sock *get_cookie_sock(struct sock *sk, struct sk_buff *skb,
* The lowest 4 bits are for snd_wscale
* The next 4 lsb are for rcv_wscale
* The next lsb is for sack_ok
+ *
+ * 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)
{
/* echoed timestamp, 9 lowest bits contain options */
u32 options = tcp_opt->rcv_tsecr & TSMASK;
+ if (!tcp_opt->saw_tstamp) {
+ tcp_clear_options(tcp_opt);
+ return true;
+ }
+
+ if (!sysctl_tcp_timestamps)
+ return false;
+
tcp_opt->snd_wscale = options & 0xf;
options >>= 4;
tcp_opt->rcv_wscale = options & 0xf;
tcp_opt->sack_ok = (options >> 4) & 0x1;
- if (tcp_opt->sack_ok)
- tcp_sack_reset(tcp_opt);
+ if (tcp_opt->sack_ok && !sysctl_tcp_sack)
+ return false;
- if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale)
+ if (tcp_opt->snd_wscale || tcp_opt->rcv_wscale) {
tcp_opt->wscale_ok = 1;
+ return sysctl_tcp_window_scaling != 0;
+ }
+ return true;
}
EXPORT_SYMBOL(cookie_check_timestamp);
@@ -281,8 +294,8 @@ 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 (tcp_opt.saw_tstamp)
- cookie_check_timestamp(&tcp_opt);
+ if (!cookie_check_timestamp(&tcp_opt))
+ goto out;
ret = NULL;
req = inet_reqsk_alloc(&tcp_request_sock_ops); /* for safety */
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 70d330f..c7ee574 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -180,8 +180,8 @@ struct sock *cookie_v6_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 (tcp_opt.saw_tstamp)
- cookie_check_timestamp(&tcp_opt);
+ if (!cookie_check_timestamp(&tcp_opt))
+ goto out;
ret = NULL;
req = inet6_reqsk_alloc(&tcp6_request_sock_ops);
--
1.6.4.4
--
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