net: udp: introduce UDP_MIB_MEMERRORS for udp_mem

When udp_memory_allocated is at the limit, __udp_enqueue_schedule_skb
will return a -ENOBUFS, and skb will be dropped in __udp_queue_rcv_skb
without any counters being done. It's hard to find out what happened
once this happen.

So we introduce a UDP_MIB_MEMERRORS to do this job. Well, this change
looks friendly to the existing users, such as netstat:

$ netstat -u -s
Udp:
    0 packets received
    639 packets to unknown port received.
    158689 packet receive errors
    180022 packets sent
    RcvbufErrors: 20930
    MemErrors: 137759
UdpLite:
IpExt:
    InOctets: 257426235
    OutOctets: 257460598
    InNoECTPkts: 181177

v2:
- Fix some alignment problems

Signed-off-by: Menglong Dong <dong.menglong@zte.com.cn>
Link: https://lore.kernel.org/r/1604627354-43207-1-git-send-email-dong.menglong@zte.com.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/net/ipv6/proc.c b/net/ipv6/proc.c
index bbff3e02e302..d6306aa46bb1 100644
--- a/net/ipv6/proc.c
+++ b/net/ipv6/proc.c
@@ -126,6 +126,7 @@ static const struct snmp_mib snmp6_udp6_list[] = {
 	SNMP_MIB_ITEM("Udp6SndbufErrors", UDP_MIB_SNDBUFERRORS),
 	SNMP_MIB_ITEM("Udp6InCsumErrors", UDP_MIB_CSUMERRORS),
 	SNMP_MIB_ITEM("Udp6IgnoredMulti", UDP_MIB_IGNOREDMULTI),
+	SNMP_MIB_ITEM("Udp6MemErrors", UDP_MIB_MEMERRORS),
 	SNMP_MIB_SENTINEL
 };
 
@@ -137,6 +138,7 @@ static const struct snmp_mib snmp6_udplite6_list[] = {
 	SNMP_MIB_ITEM("UdpLite6RcvbufErrors", UDP_MIB_RCVBUFERRORS),
 	SNMP_MIB_ITEM("UdpLite6SndbufErrors", UDP_MIB_SNDBUFERRORS),
 	SNMP_MIB_ITEM("UdpLite6InCsumErrors", UDP_MIB_CSUMERRORS),
+	SNMP_MIB_ITEM("UdpLite6MemErrors", UDP_MIB_MEMERRORS),
 	SNMP_MIB_SENTINEL
 };