path: root/net/ipv4/tcp_ipv4.c
diff options
authorArnd Bergmann <arnd@arndb.de>2018-07-11 12:16:12 +0200
committerDavid S. Miller <davem@davemloft.net>2018-07-12 14:50:40 -0700
commitcca9bab1b72cd2296097c75f59ef11ef80461279 (patch)
tree2262a12f93e2a0977d5259bca9b74eee89f33c88 /net/ipv4/tcp_ipv4.c
parentnet/tls: Use aead_request_alloc/free for request alloc/free (diff)
tcp: use monotonic timestamps for PAWS
Using get_seconds() for timestamps is deprecated since it can lead to overflows on 32-bit systems. While the interface generally doesn't overflow until year 2106, the specific implementation of the TCP PAWS algorithm breaks in 2038 when the intermediate signed 32-bit timestamps overflow. A related problem is that the local timestamps in CLOCK_REALTIME form lead to unexpected behavior when settimeofday is called to set the system clock backwards or forwards by more than 24 days. While the first problem could be solved by using an overflow-safe method of comparing the timestamps, a nicer solution is to use a monotonic clocksource with ktime_get_seconds() that simply doesn't overflow (at least not until 136 years after boot) and that doesn't change during settimeofday(). To make 32-bit and 64-bit architectures behave the same way here, and also save a few bytes in the tcp_options_received structure, I'm changing the type to a 32-bit integer, which is now safe on all architectures. Finally, the ts_recent_stamp field also (confusingly) gets used to store a jiffies value in tcp_synq_overflow()/tcp_synq_no_recent_overflow(). This is currently safe, but changing the type to 32-bit requires some small changes there to keep it working. Signed-off-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/tcp_ipv4.c')
1 files changed, 2 insertions, 1 deletions
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index bea17f1e8302..dc415c66a33a 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -155,7 +155,8 @@ int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
and use initial timestamp retrieved from peer table.
if (tcptw->tw_ts_recent_stamp &&
- (!twp || (reuse && get_seconds() - tcptw->tw_ts_recent_stamp > 1))) {
+ (!twp || (reuse && time_after32(ktime_get_seconds(),
+ tcptw->tw_ts_recent_stamp)))) {
tp->write_seq = tcptw->tw_snd_nxt + 65535 + 2;
if (tp->write_seq == 0)
tp->write_seq = 1;