From 7f1f2f3f518eace6ee08a00158189aaf571f3dcb Mon Sep 17 00:00:00 2001 From: David Gibson Date: Thu, 17 Nov 2022 16:59:01 +1100 Subject: [PATCH] tcp: Fix small errors in tcp_seq_init() time handling It looks like tcp_seq_init() is supposed to advance the sequence number by one every 32ns. However we only right shift the ns part of the timespec not the seconds part, meaning that we'll advance by an extra 32 steps on each second. I don't know if that's exploitable in any way, but it doesn't appear to be the intent, nor what RFC 6528 suggests. In addition, we convert from seconds to nanoseconds with a multiplication by '1E9'. In C '1E9' is a floating point constant, forcing a conversion to floating point and back for what should be an integer calculation (confirmed with objdump and Makefile default compiler flags). Spell out 1000000000 in full to avoid that. Signed-off-by: David Gibson Signed-off-by: Stefano Brivio --- tcp.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tcp.c b/tcp.c index dabcbc4..559e271 100644 --- a/tcp.c +++ b/tcp.c @@ -1957,8 +1957,8 @@ static void tcp_seq_init(const struct ctx *c, struct tcp_tap_conn *conn, seq = siphash_36b((uint8_t *)&in, c->tcp.hash_secret); - ns = now->tv_sec * 1E9; - ns += now->tv_nsec >> 5; /* 32ns ticks, overflows 32 bits every 137s */ + /* 32ns ticks, overflows 32 bits every 137s */ + ns = (now->tv_sec * 1000000000 + now->tv_nsec) >> 5; conn->seq_to_tap = seq + ns; }