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authorEric Dumazet <edumazet@google.com>2015-05-14 14:26:56 -0700
committerDavid S. Miller <davem@davemloft.net>2015-05-14 22:32:17 -0400
commit264ea103a7473f51aced838e68ed384ea2c759f5 (patch)
tree0f8366835d004fb0ee387d876f6c4b301a0ff89e /include/net/tcp.h
parentc24a59649f3c8f4f78adc2d0e31423fa883b012b (diff)
downloadop-kernel-dev-264ea103a7473f51aced838e68ed384ea2c759f5.zip
op-kernel-dev-264ea103a7473f51aced838e68ed384ea2c759f5.tar.gz
tcp: syncookies: extend validity range
Now we allow storing more request socks per listener, we might hit syncookie mode less often and hit following bug in our stack : When we send a burst of syncookies, then exit this mode, tcp_synq_no_recent_overflow() can return false if the ACK packets coming from clients are coming three seconds after the end of syncookie episode. This is a way too strong requirement and conflicts with rest of syncookie code which allows ACK to be aged up to 2 minutes. Perfectly valid ACK packets are dropped just because clients might be in a crowded wifi environment or on another planet. So let's fix this, and also change tcp_synq_overflow() to not dirty a cache line for every syncookie we send, as we are under attack. Signed-off-by: Eric Dumazet <edumazet@google.com> Acked-by: Florian Westphal <fw@strlen.de> Acked-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net/tcp.h')
-rw-r--r--include/net/tcp.h38
1 files changed, 24 insertions, 14 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h
index b8ea128..7ace6ac 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -326,18 +326,6 @@ static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
bool tcp_check_oom(struct sock *sk, int shift);
-/* syncookies: remember time of last synqueue overflow */
-static inline void tcp_synq_overflow(struct sock *sk)
-{
- tcp_sk(sk)->rx_opt.ts_recent_stamp = jiffies;
-}
-
-/* syncookies: no recent synqueue overflow on this listening socket? */
-static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
-{
- unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
- return time_after(jiffies, last_overflow + TCP_TIMEOUT_FALLBACK);
-}
extern struct proto tcp_prot;
@@ -483,13 +471,35 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
* i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
* the counter advances immediately after a cookie is generated).
*/
-#define MAX_SYNCOOKIE_AGE 2
+#define MAX_SYNCOOKIE_AGE 2
+#define TCP_SYNCOOKIE_PERIOD (60 * HZ)
+#define TCP_SYNCOOKIE_VALID (MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
+
+/* syncookies: remember time of last synqueue overflow
+ * But do not dirty this field too often (once per second is enough)
+ */
+static inline void tcp_synq_overflow(struct sock *sk)
+{
+ unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
+ unsigned long now = jiffies;
+
+ if (time_after(now, last_overflow + HZ))
+ tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
+}
+
+/* syncookies: no recent synqueue overflow on this listening socket? */
+static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
+{
+ unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
+
+ return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
+}
static inline u32 tcp_cookie_time(void)
{
u64 val = get_jiffies_64();
- do_div(val, 60 * HZ);
+ do_div(val, TCP_SYNCOOKIE_PERIOD);
return val;
}
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