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syncookies: check decoded options against sysctl settings

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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.

Also remove an unneeded call to tcp_sack_reset() in
cookie_check_timestamp: Both call sites (cookie_v4_check,
cookie_v6_check) zero "struct tcp_options_received", hand it to
tcp_parse_options() (which does not change tcp_opt->num_sacks/dsack)
and then call cookie_check_timestamp().

Even if num_sacks/dsacks were changed, the structure is allocated on
the stack and after cookie_check_timestamp returns only a few selected
members are copied to the inet_request_sock.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Florian Westphal
2010-06-16 14:42:15 -07:00
committed by David S. Miller
parent 317fe0e6c5
commit 8c76368174
3 changed files with 22 additions and 9 deletions
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2
include/net/tcp.h
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@@ -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);