snmp: 64bit ipstats_mib for all arches

/proc/net/snmp and /proc/net/netstat expose SNMP counters.

Width of these counters is either 32 or 64 bits, depending on the size
of "unsigned long" in kernel.

This means user program parsing these files must already be prepared to
deal with 64bit values, regardless of user program being 32 or 64 bit.

This patch introduces 64bit snmp values for IPSTAT mib, where some
counters can wrap pretty fast if they are 32bit wide.

# netstat -s|egrep "InOctets|OutOctets"
    InOctets: 244068329096
    OutOctets: 244069348848

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 45 insertions, 6 deletions

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 640db9b..3ceb025 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -1427,6 +1427,42 @@ unsigned long snmp_fold_field(void __percpu *mib[], int offt)
 }
 EXPORT_SYMBOL_GPL(snmp_fold_field);
 
+#if BITS_PER_LONG==32
+
+u64 snmp_fold_field64(void __percpu *mib[], int offt, size_t syncp_offset)
+{
+	u64 res = 0;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		void *bhptr, *userptr;
+		struct u64_stats_sync *syncp;
+		u64 v_bh, v_user;
+		unsigned int start;
+
+		/* first mib used by softirq context, we must use _bh() accessors */
+		bhptr = per_cpu_ptr(SNMP_STAT_BHPTR(mib), cpu);
+		syncp = (struct u64_stats_sync *)(bhptr + syncp_offset);
+		do {
+			start = u64_stats_fetch_begin_bh(syncp);
+			v_bh = *(((u64 *) bhptr) + offt);
+		} while (u64_stats_fetch_retry_bh(syncp, start));
+
+		/* second mib used in USER context */
+		userptr = per_cpu_ptr(SNMP_STAT_USRPTR(mib), cpu);
+		syncp = (struct u64_stats_sync *)(userptr + syncp_offset);
+		do {
+			start = u64_stats_fetch_begin(syncp);
+			v_user = *(((u64 *) userptr) + offt);
+		} while (u64_stats_fetch_retry(syncp, start));
+
+		res += v_bh + v_user;
+	}
+	return res;
+}
+EXPORT_SYMBOL_GPL(snmp_fold_field64);
+#endif
+
 int snmp_mib_init(void __percpu *ptr[2], size_t mibsize, size_t align)
 {
 	BUG_ON(ptr == NULL);
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index e320ca6..4ae1f20 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -343,10 +343,12 @@ static int snmp_seq_show(struct seq_file *seq, void *v)
 		   IPV4_DEVCONF_ALL(net, FORWARDING) ? 1 : 2,
 		   sysctl_ip_default_ttl);
 
+	BUILD_BUG_ON(offsetof(struct ipstats_mib, mibs) != 0);
 	for (i = 0; snmp4_ipstats_list[i].name != NULL; i++)
-		seq_printf(seq, " %lu",
-			   snmp_fold_field((void __percpu **)net->mib.ip_statistics,
-					   snmp4_ipstats_list[i].entry));
+		seq_printf(seq, " %llu",
+			   snmp_fold_field64((void __percpu **)net->mib.ip_statistics,
+					     snmp4_ipstats_list[i].entry,
+					     offsetof(struct ipstats_mib, syncp)));
 
 	icmp_put(seq);	/* RFC 2011 compatibility */
 	icmpmsg_put(seq);
@@ -432,9 +434,10 @@ static int netstat_seq_show(struct seq_file *seq, void *v)
 
 	seq_puts(seq, "\nIpExt:");
 	for (i = 0; snmp4_ipextstats_list[i].name != NULL; i++)
-		seq_printf(seq, " %lu",
-			   snmp_fold_field((void __percpu **)net->mib.ip_statistics,
-					   snmp4_ipextstats_list[i].entry));
+		seq_printf(seq, " %llu",
+			   snmp_fold_field64((void __percpu **)net->mib.ip_statistics,
+					     snmp4_ipextstats_list[i].entry,
+					     offsetof(struct ipstats_mib, syncp)));
 
 	seq_putc(seq, '\n');
 	return 0;