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>

diff --git a/drivers/crypto/chelsio/chtls/chtls_cm.c b/drivers/crypto/chelsio/chtls/chtls_cm.c
index 2bb6f0380758829077a789f8eb26932e108a360c..0997e166ea57755c4d0178702995cce489b06d7e 100644 (file)
--- a/drivers/crypto/chelsio/chtls/chtls_cm.c
+++ b/drivers/crypto/chelsio/chtls/chtls_cm.c
@@ -1673,7 +1673,7 @@ static void chtls_timewait(struct sock *sk)
        struct tcp_sock *tp = tcp_sk(sk);
 
        tp->rcv_nxt++;
-       tp->rx_opt.ts_recent_stamp = get_seconds();
+       tp->rx_opt.ts_recent_stamp = ktime_get_seconds();
        tp->srtt_us = 0;
        tcp_time_wait(sk, TCP_TIME_WAIT, 0);
 }

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 3dbea6610304627e590577ef2e8b7319c1e87c9c..58a8d7d713549bee88113a0a3373dd8cc055d72d 100644 (file)
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -89,7 +89,7 @@ struct tcp_sack_block {
 
 struct tcp_options_received {
 /*     PAWS/RTTM data  */
-       long    ts_recent_stamp;/* Time we stored ts_recent (for aging) */
+       int     ts_recent_stamp;/* Time we stored ts_recent (for aging) */
        u32     ts_recent;      /* Time stamp to echo next              */
        u32     rcv_tsval;      /* Time stamp value                     */
        u32     rcv_tsecr;      /* Time stamp echo reply                */
@@ -426,7 +426,7 @@ struct tcp_timewait_sock {
        /* The time we sent the last out-of-window ACK: */
        u32                       tw_last_oow_ack_time;
 
-       long                      tw_ts_recent_stamp;
+       int                       tw_ts_recent_stamp;
 #ifdef CONFIG_TCP_MD5SIG
        struct tcp_md5sig_key     *tw_md5_key;
 #endif

diff --git a/include/net/tcp.h b/include/net/tcp.h
index f6cb20e6e524018e0e98d8e0dce342f27dae660b..582304955087f37cf36e48771f699e1421e2869a 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -472,19 +472,20 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
  */
 static inline void tcp_synq_overflow(const struct sock *sk)
 {
-       unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
-       unsigned long now = jiffies;
+       unsigned int last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
+       unsigned int now = jiffies;
 
-       if (time_after(now, last_overflow + HZ))
+       if (time_after32(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;
+       unsigned int last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
+       unsigned int now = jiffies;
 
-       return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
+       return time_after32(now, last_overflow + TCP_SYNCOOKIE_VALID);
 }
 
 static inline u32 tcp_cookie_time(void)
@@ -1375,7 +1376,8 @@ static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
 {
        if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
                return true;
-       if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
+       if (unlikely(!time_before32(ktime_get_seconds(),
+                                   rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS)))
                return true;
        /*
         * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
@@ -1405,7 +1407,8 @@ static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
 
           However, we can relax time bounds for RST segments to MSL.
         */
-       if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
+       if (rst && !time_before32(ktime_get_seconds(),
+                                 rx_opt->ts_recent_stamp + TCP_PAWS_MSL))
                return false;
        return true;
 }

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 814ea43dd12f4552f4c9aa07d0f66cd889347a01..d3b6390ecf2311215e6a9698f423754d580f28f4 100644 (file)
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3462,7 +3462,7 @@ static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb)
 static void tcp_store_ts_recent(struct tcp_sock *tp)
 {
        tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
-       tp->rx_opt.ts_recent_stamp = get_seconds();
+       tp->rx_opt.ts_recent_stamp = ktime_get_seconds();
 }
 
 static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index bea17f1e8302585d70c1e0108ae1c33d149230d8..dc415c66a33a15d4e5d81a8999500e4cabbf12b3 100644 (file)
--- 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;

diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index dac5893a52b4520d86ed2fcadbfb561a559fcd3d..75ef332a7caf44de619acf030977eba01565c70a 100644 (file)
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -144,7 +144,7 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
                tw->tw_substate   = TCP_TIME_WAIT;
                tcptw->tw_rcv_nxt = TCP_SKB_CB(skb)->end_seq;
                if (tmp_opt.saw_tstamp) {
-                       tcptw->tw_ts_recent_stamp = get_seconds();
+                       tcptw->tw_ts_recent_stamp = ktime_get_seconds();
                        tcptw->tw_ts_recent       = tmp_opt.rcv_tsval;
                }
 
@@ -189,7 +189,7 @@ kill:
 
                if (tmp_opt.saw_tstamp) {
                        tcptw->tw_ts_recent       = tmp_opt.rcv_tsval;
-                       tcptw->tw_ts_recent_stamp = get_seconds();
+                       tcptw->tw_ts_recent_stamp = ktime_get_seconds();
                }
 
                inet_twsk_put(tw);
@@ -537,7 +537,7 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 
        if (newtp->rx_opt.tstamp_ok) {
                newtp->rx_opt.ts_recent = req->ts_recent;
-               newtp->rx_opt.ts_recent_stamp = get_seconds();
+               newtp->rx_opt.ts_recent_stamp = ktime_get_seconds();
                newtp->tcp_header_len = sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
        } else {
                newtp->rx_opt.ts_recent_stamp = 0;
@@ -603,7 +603,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
                         * it can be estimated (approximately)
                         * from another data.
                         */
-                       tmp_opt.ts_recent_stamp = get_seconds() - ((TCP_TIMEOUT_INIT/HZ)<<req->num_timeout);
+                       tmp_opt.ts_recent_stamp = ktime_get_seconds() - ((TCP_TIMEOUT_INIT/HZ)<<req->num_timeout);
                        paws_reject = tcp_paws_reject(&tmp_opt, th->rst);
                }
        }