From 25429d7b7dca01dc4f17205de023a30ca09390d0 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Thu, 1 Dec 2016 11:32:07 +0100 Subject: tcp: allow to turn tcp timestamp randomization off Eric says: "By looking at tcpdump, and TS val of xmit packets of multiple flows, we can deduct the relative qdisc delays (think of fq pacing). This should work even if we have one flow per remote peer." Having random per flow (or host) offsets doesn't allow that anymore so add a way to turn this off. Suggested-by: Eric Dumazet Signed-off-by: Florian Westphal Acked-by: Yuchung Cheng Signed-off-by: David S. Miller --- net/core/secure_seq.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'net/core') diff --git a/net/core/secure_seq.c b/net/core/secure_seq.c index a8d6062cbb4a..88a8e429fc3e 100644 --- a/net/core/secure_seq.c +++ b/net/core/secure_seq.c @@ -12,6 +12,7 @@ #include #if IS_ENABLED(CONFIG_IPV6) || IS_ENABLED(CONFIG_INET) +#include #define NET_SECRET_SIZE (MD5_MESSAGE_BYTES / 4) static u32 net_secret[NET_SECRET_SIZE] ____cacheline_aligned; @@ -58,7 +59,7 @@ u32 secure_tcpv6_sequence_number(const __be32 *saddr, const __be32 *daddr, md5_transform(hash, secret); - *tsoff = hash[1]; + *tsoff = sysctl_tcp_timestamps == 1 ? hash[1] : 0; return seq_scale(hash[0]); } EXPORT_SYMBOL(secure_tcpv6_sequence_number); @@ -100,7 +101,7 @@ u32 secure_tcp_sequence_number(__be32 saddr, __be32 daddr, md5_transform(hash, net_secret); - *tsoff = hash[1]; + *tsoff = sysctl_tcp_timestamps == 1 ? hash[1] : 0; return seq_scale(hash[0]); } -- cgit v1.2.3