net: ipv4: Convert IP network timestamps to be y2038 safe

ICMP timestamp messages and IP source route options require
timestamps to be in milliseconds modulo 24 hours from
midnight UT format.

Add inet_current_timestamp() function to support this. The function
returns the required timestamp in network byte order.

Timestamp calculation is also changed to call ktime_get_real_ts64()
which uses struct timespec64. struct timespec64 is y2038 safe.
Previously it called getnstimeofday() which uses struct timespec.
struct timespec is not y2038 safe.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: James Morris <jmorris@namei.org>
Cc: Patrick McHardy <kaber@trash.net>
Acked-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 0 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 209d1ed28954..0cc923f83e10 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1380,6 +1380,32 @@ out:
 	return pp;
 }
 
+#define SECONDS_PER_DAY	86400
+
+/* inet_current_timestamp - Return IP network timestamp
+ *
+ * Return milliseconds since midnight in network byte order.
+ */
+__be32 inet_current_timestamp(void)
+{
+	u32 secs;
+	u32 msecs;
+	struct timespec64 ts;
+
+	ktime_get_real_ts64(&ts);
+
+	/* Get secs since midnight. */
+	(void)div_u64_rem(ts.tv_sec, SECONDS_PER_DAY, &secs);
+	/* Convert to msecs. */
+	msecs = secs * MSEC_PER_SEC;
+	/* Convert nsec to msec. */
+	msecs += (u32)ts.tv_nsec / NSEC_PER_MSEC;
+
+	/* Convert to network byte order. */
+	return htons(msecs);
+}
+EXPORT_SYMBOL(inet_current_timestamp);
+
 int inet_recv_error(struct sock *sk, struct msghdr *msg, int len, int *addr_len)
 {
 	if (sk->sk_family == AF_INET)