[PATCH v2 1/3] net: ipv4: Convert IP network timestamps to be y2038 safe

[Deepa Dinamani <deepa.kernel@gmail.com>]

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>
---
 include/net/ip.h      |  2 ++
 net/ipv4/af_inet.c    | 26 ++++++++++++++++++++++++++
 net/ipv4/icmp.c       |  5 +----
 net/ipv4/ip_options.c | 14 ++++++--------
 4 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index 1a98f1c..5d3a9eb 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -240,6 +240,8 @@ static inline int inet_is_local_reserved_port(struct net *net, int port)
 }
 #endif
 
+__be32 inet_current_timestamp(void);
+
 /* From inetpeer.c */
 extern int inet_peer_threshold;
 extern int inet_peer_minttl;
diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index eade66d..408e2b3 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1386,6 +1386,32 @@ 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)
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 36e2697..6333489 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -931,7 +931,6 @@ static bool icmp_echo(struct sk_buff *skb)
  */
 static bool icmp_timestamp(struct sk_buff *skb)
 {
-	struct timespec tv;
 	struct icmp_bxm icmp_param;
 	/*
 	 *	Too short.
@@ -942,9 +941,7 @@ static bool icmp_timestamp(struct sk_buff *skb)
 	/*
 	 *	Fill in the current time as ms since midnight UT:
 	 */
-	getnstimeofday(&tv);
-	icmp_param.data.times[1] = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC +
-					 tv.tv_nsec / NSEC_PER_MSEC);
+	icmp_param.data.times[1] = inet_current_timestamp();
 	icmp_param.data.times[2] = icmp_param.data.times[1];
 	if (skb_copy_bits(skb, 0, &icmp_param.data.times[0], 4))
 		BUG();
diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c
index bd24679..4d158ff 100644
--- a/net/ipv4/ip_options.c
+++ b/net/ipv4/ip_options.c
@@ -58,10 +58,9 @@ void ip_options_build(struct sk_buff *skb, struct ip_options *opt,
 		if (opt->ts_needaddr)
 			ip_rt_get_source(iph+opt->ts+iph[opt->ts+2]-9, skb, rt);
 		if (opt->ts_needtime) {
-			struct timespec tv;
 			__be32 midtime;
-			getnstimeofday(&tv);
-			midtime = htonl((tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC);
+
+			midtime = inet_current_timestamp();
 			memcpy(iph+opt->ts+iph[opt->ts+2]-5, &midtime, 4);
 		}
 		return;
@@ -415,11 +414,10 @@ int ip_options_compile(struct net *net,
 					break;
 				}
 				if (timeptr) {
-					struct timespec tv;
-					u32  midtime;
-					getnstimeofday(&tv);
-					midtime = (tv.tv_sec % 86400) * MSEC_PER_SEC + tv.tv_nsec / NSEC_PER_MSEC;
-					put_unaligned_be32(midtime, timeptr);
+					__be32 midtime;
+
+					midtime = inet_current_timestamp();
+					memcpy(timeptr, &midtime, 4);
 					opt->is_changed = 1;
 				}
 			} else if ((optptr[3]&0xF) != IPOPT_TS_PRESPEC) {
-- 
1.9.1