net: Add MIB counters for checksum errors

Add MIB counters for checksum errors in IP layer,
and TCP/UDP/ICMP layers, to help diagnose problems.

$ nstat -a | grep Csum
IcmpInCsumErrors 72 0.0
TcpInCsumErrors 382 0.0
UdpInCsumErrors 463221 0.0
Icmp6InCsumErrors 75 0.0
Udp6InCsumErrors 173442 0.0
IpExtInCsumErrors 10884 0.0

Signed-off-by: Eric Dumazet <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

include/uapi/linux/snmp.h

···
 	IPSTATS_MIB_OUTMCASTOCTETS,		/* OutMcastOctets */
 	IPSTATS_MIB_INBCASTOCTETS,		/* InBcastOctets */
 	IPSTATS_MIB_OUTBCASTOCTETS,		/* OutBcastOctets */
+	IPSTATS_MIB_CSUMERRORS,			/* InCsumErrors */
 	__IPSTATS_MIB_MAX
 };
 
···
 	ICMP_MIB_OUTTIMESTAMPREPS,		/* OutTimestampReps */
 	ICMP_MIB_OUTADDRMASKS,			/* OutAddrMasks */
 	ICMP_MIB_OUTADDRMASKREPS,		/* OutAddrMaskReps */
+	ICMP_MIB_CSUMERRORS,			/* InCsumErrors */
 	__ICMP_MIB_MAX
 };
 
···
 	ICMP6_MIB_INERRORS,			/* InErrors */
 	ICMP6_MIB_OUTMSGS,			/* OutMsgs */
 	ICMP6_MIB_OUTERRORS,			/* OutErrors */
+	ICMP6_MIB_CSUMERRORS,			/* InCsumErrors */
 	__ICMP6_MIB_MAX
 };
 
···
 	TCP_MIB_RETRANSSEGS,			/* RetransSegs */
 	TCP_MIB_INERRS,				/* InErrs */
 	TCP_MIB_OUTRSTS,			/* OutRsts */
+	TCP_MIB_CSUMERRORS,			/* InCsumErrors */
 	__TCP_MIB_MAX
 };
 
···
 	UDP_MIB_OUTDATAGRAMS,			/* OutDatagrams */
 	UDP_MIB_RCVBUFERRORS,			/* RcvbufErrors */
 	UDP_MIB_SNDBUFERRORS,			/* SndbufErrors */
+	UDP_MIB_CSUMERRORS,			/* InCsumErrors */
 	__UDP_MIB_MAX
 };
 

net/ipv4/icmp.c

···
 	case CHECKSUM_NONE:
 		skb->csum = 0;
 		if (__skb_checksum_complete(skb))
-			goto error;
+			goto csum_error;
 	}
 
 	if (!pskb_pull(skb, sizeof(*icmph)))
···
 drop:
 	kfree_skb(skb);
 	return 0;
+csum_error:
+	ICMP_INC_STATS_BH(net, ICMP_MIB_CSUMERRORS);
 error:
 	ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
 	goto drop;

net/ipv4/ip_input.c

···
 	iph = ip_hdr(skb);
 
 	if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
-		goto inhdr_error;
+		goto csum_error;
 
 	len = ntohs(iph->tot_len);
 	if (skb->len < len) {
···
 	return NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, dev, NULL,
 		       ip_rcv_finish);
 
+csum_error:
+	IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_CSUMERRORS);
 inhdr_error:
 	IP_INC_STATS_BH(dev_net(dev), IPSTATS_MIB_INHDRERRORS);
 drop:

net/ipv4/proc.c

···
 	SNMP_MIB_ITEM("OutMcastOctets", IPSTATS_MIB_OUTMCASTOCTETS),
 	SNMP_MIB_ITEM("InBcastOctets", IPSTATS_MIB_INBCASTOCTETS),
 	SNMP_MIB_ITEM("OutBcastOctets", IPSTATS_MIB_OUTBCASTOCTETS),
+	SNMP_MIB_ITEM("InCsumErrors", IPSTATS_MIB_CSUMERRORS),
 	SNMP_MIB_SENTINEL
 };
 
···
 	SNMP_MIB_ITEM("RetransSegs", TCP_MIB_RETRANSSEGS),
 	SNMP_MIB_ITEM("InErrs", TCP_MIB_INERRS),
 	SNMP_MIB_ITEM("OutRsts", TCP_MIB_OUTRSTS),
+	SNMP_MIB_ITEM("InCsumErrors", TCP_MIB_CSUMERRORS),
 	SNMP_MIB_SENTINEL
 };
 
···
 	SNMP_MIB_ITEM("OutDatagrams", UDP_MIB_OUTDATAGRAMS),
 	SNMP_MIB_ITEM("RcvbufErrors", UDP_MIB_RCVBUFERRORS),
 	SNMP_MIB_ITEM("SndbufErrors", UDP_MIB_SNDBUFERRORS),
+	SNMP_MIB_ITEM("InCsumErrors", UDP_MIB_CSUMERRORS),
 	SNMP_MIB_SENTINEL
 };
 
···
 	struct net *net = seq->private;
 	atomic_long_t *ptr = net->mib.icmpmsg_statistics->mibs;
 
-	seq_puts(seq, "\nIcmp: InMsgs InErrors");
+	seq_puts(seq, "\nIcmp: InMsgs InErrors InCsumErrors");
 	for (i=0; icmpmibmap[i].name != NULL; i++)
 		seq_printf(seq, " In%s", icmpmibmap[i].name);
 	seq_printf(seq, " OutMsgs OutErrors");
 	for (i=0; icmpmibmap[i].name != NULL; i++)
 		seq_printf(seq, " Out%s", icmpmibmap[i].name);
-	seq_printf(seq, "\nIcmp: %lu %lu",
+	seq_printf(seq, "\nIcmp: %lu %lu %lu",
 		snmp_fold_field((void __percpu **) net->mib.icmp_statistics, ICMP_MIB_INMSGS),
-		snmp_fold_field((void __percpu **) net->mib.icmp_statistics, ICMP_MIB_INERRORS));
+		snmp_fold_field((void __percpu **) net->mib.icmp_statistics, ICMP_MIB_INERRORS),
+		snmp_fold_field((void __percpu **) net->mib.icmp_statistics, ICMP_MIB_CSUMERRORS));
 	for (i=0; icmpmibmap[i].name != NULL; i++)
 		seq_printf(seq, " %lu",
 			   atomic_long_read(ptr + icmpmibmap[i].index));

net/ipv4/tcp_input.c

···
 	return 0;
 
 csum_error:
+	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_CSUMERRORS);
 	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
 
 discard:

net/ipv4/tcp_ipv4.c

···
 	return 0;
 
 csum_err:
+	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_CSUMERRORS);
 	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
 	goto discard;
 }
···
 	 * provided case of th->doff==0 is eliminated.
 	 * So, we defer the checks. */
 	if (!skb_csum_unnecessary(skb) && tcp_v4_checksum_init(skb))
-		goto bad_packet;
+		goto csum_error;
 
 	th = tcp_hdr(skb);
 	iph = ip_hdr(skb);
···
 		goto discard_it;
 
 	if (skb->len < (th->doff << 2) || tcp_checksum_complete(skb)) {
+csum_error:
+		TCP_INC_STATS_BH(net, TCP_MIB_CSUMERRORS);
 bad_packet:
 		TCP_INC_STATS_BH(net, TCP_MIB_INERRS);
 	} else {
···
 		goto discard_it;
 	}
 
-	if (skb->len < (th->doff << 2) || tcp_checksum_complete(skb)) {
-		TCP_INC_STATS_BH(net, TCP_MIB_INERRS);
+	if (skb->len < (th->doff << 2)) {
 		inet_twsk_put(inet_twsk(sk));
-		goto discard_it;
+		goto bad_packet;
+	}
+	if (tcp_checksum_complete(skb)) {
+		inet_twsk_put(inet_twsk(sk));
+		goto csum_error;
 	}
 	switch (tcp_timewait_state_process(inet_twsk(sk), skb, th)) {
 	case TCP_TW_SYN: {

net/ipv4/tcp_output.c

···
 
 	tp->packets_out += tcp_skb_pcount(skb);
 	if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
-	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)
+	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
 		tcp_rearm_rto(sk);
+	}
 }
 
 /* SND.NXT, if window was not shrunk.

net/ipv4/udp.c

···
 	spin_lock_bh(&rcvq->lock);
 	while ((skb = skb_peek(rcvq)) != NULL &&
 		udp_lib_checksum_complete(skb)) {
+		UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_CSUMERRORS,
+				 IS_UDPLITE(sk));
 		UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS,
 				 IS_UDPLITE(sk));
 		atomic_inc(&sk->sk_drops);
···
 
 csum_copy_err:
 	slow = lock_sock_fast(sk);
-	if (!skb_kill_datagram(sk, skb, flags))
+	if (!skb_kill_datagram(sk, skb, flags)) {
+		UDP_INC_STATS_USER(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
 		UDP_INC_STATS_USER(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
+	}
 	unlock_sock_fast(sk, slow);
 
 	if (noblock)
···
 
 	if (rcu_access_pointer(sk->sk_filter) &&
 	    udp_lib_checksum_complete(skb))
-		goto drop;
+		goto csum_error;
 
 
 	if (sk_rcvqueues_full(sk, skb, sk->sk_rcvbuf))
···
 
 	return rc;
 
+csum_error:
+	UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
 drop:
 	UDP_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
 	atomic_inc(&sk->sk_drops);
···
 		       proto == IPPROTO_UDPLITE ? "Lite" : "",
 		       &saddr, ntohs(uh->source), &daddr, ntohs(uh->dest),
 		       ulen);
+	UDP_INC_STATS_BH(net, UDP_MIB_CSUMERRORS, proto == IPPROTO_UDPLITE);
 drop:
 	UDP_INC_STATS_BH(net, UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
 	kfree_skb(skb);

net/ipv6/icmp.c

···
 		if (__skb_checksum_complete(skb)) {
 			LIMIT_NETDEBUG(KERN_DEBUG "ICMPv6 checksum failed [%pI6 > %pI6]\n",
 				       saddr, daddr);
-			goto discard_it;
+			goto csum_error;
 		}
 	}
 
···
 	kfree_skb(skb);
 	return 0;
 
+csum_error:
+	ICMP6_INC_STATS_BH(dev_net(dev), idev, ICMP6_MIB_CSUMERRORS);
 discard_it:
 	ICMP6_INC_STATS_BH(dev_net(dev), idev, ICMP6_MIB_INERRORS);
 drop_no_count:

net/ipv6/proc.c

···
 	SNMP_MIB_ITEM("Ip6OutMcastOctets", IPSTATS_MIB_OUTMCASTOCTETS),
 	SNMP_MIB_ITEM("Ip6InBcastOctets", IPSTATS_MIB_INBCASTOCTETS),
 	SNMP_MIB_ITEM("Ip6OutBcastOctets", IPSTATS_MIB_OUTBCASTOCTETS),
+	SNMP_MIB_ITEM("InCsumErrors", IPSTATS_MIB_CSUMERRORS),
 	SNMP_MIB_SENTINEL
 };
 
···
 	SNMP_MIB_ITEM("Icmp6InErrors", ICMP6_MIB_INERRORS),
 	SNMP_MIB_ITEM("Icmp6OutMsgs", ICMP6_MIB_OUTMSGS),
 	SNMP_MIB_ITEM("Icmp6OutErrors", ICMP6_MIB_OUTERRORS),
+	SNMP_MIB_ITEM("Icmp6InCsumErrors", ICMP6_MIB_CSUMERRORS),
 	SNMP_MIB_SENTINEL
 };
 
···
 	SNMP_MIB_ITEM("Udp6OutDatagrams", UDP_MIB_OUTDATAGRAMS),
 	SNMP_MIB_ITEM("Udp6RcvbufErrors", UDP_MIB_RCVBUFERRORS),
 	SNMP_MIB_ITEM("Udp6SndbufErrors", UDP_MIB_SNDBUFERRORS),
+	SNMP_MIB_ITEM("Udp6InCsumErrors", UDP_MIB_CSUMERRORS),
 	SNMP_MIB_SENTINEL
 };
 
···
 	SNMP_MIB_ITEM("UdpLite6OutDatagrams", UDP_MIB_OUTDATAGRAMS),
 	SNMP_MIB_ITEM("UdpLite6RcvbufErrors", UDP_MIB_RCVBUFERRORS),
 	SNMP_MIB_ITEM("UdpLite6SndbufErrors", UDP_MIB_SNDBUFERRORS),
+	SNMP_MIB_ITEM("UdpLite6InCsumErrors", UDP_MIB_CSUMERRORS),
 	SNMP_MIB_SENTINEL
 };
 

net/ipv6/tcp_ipv6.c

···
 	kfree_skb(skb);
 	return 0;
 csum_err:
+	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_CSUMERRORS);
 	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
 	goto discard;
 
···
 		goto discard_it;
 
 	if (!skb_csum_unnecessary(skb) && tcp_v6_checksum_init(skb))
-		goto bad_packet;
+		goto csum_error;
 
 	th = tcp_hdr(skb);
 	hdr = ipv6_hdr(skb);
···
 		goto discard_it;
 
 	if (skb->len < (th->doff<<2) || tcp_checksum_complete(skb)) {
+csum_error:
+		TCP_INC_STATS_BH(net, TCP_MIB_CSUMERRORS);
 bad_packet:
 		TCP_INC_STATS_BH(net, TCP_MIB_INERRS);
 	} else {
···
 	}
 
 discard_it:
-
-	/*
-	 *	Discard frame
-	 */
-
 	kfree_skb(skb);
 	return 0;
 
···
 		goto discard_it;
 	}
 
-	if (skb->len < (th->doff<<2) || tcp_checksum_complete(skb)) {
-		TCP_INC_STATS_BH(net, TCP_MIB_INERRS);
+	if (skb->len < (th->doff<<2)) {
 		inet_twsk_put(inet_twsk(sk));
-		goto discard_it;
+		goto bad_packet;
+	}
+	if (tcp_checksum_complete(skb)) {
+		inet_twsk_put(inet_twsk(sk));
+		goto csum_error;
 	}
 
 	switch (tcp_timewait_state_process(inet_twsk(sk), skb, th)) {

net/ipv6/udp.c

···
 csum_copy_err:
 	slow = lock_sock_fast(sk);
 	if (!skb_kill_datagram(sk, skb, flags)) {
-		if (is_udp4)
+		if (is_udp4) {
+			UDP_INC_STATS_USER(sock_net(sk),
+					UDP_MIB_CSUMERRORS, is_udplite);
 			UDP_INC_STATS_USER(sock_net(sk),
 					UDP_MIB_INERRORS, is_udplite);
-		else
+		} else {
+			UDP6_INC_STATS_USER(sock_net(sk),
+					UDP_MIB_CSUMERRORS, is_udplite);
 			UDP6_INC_STATS_USER(sock_net(sk),
 					UDP_MIB_INERRORS, is_udplite);
+		}
 	}
 	unlock_sock_fast(sk, slow);
 
···
 
 	if (rcu_access_pointer(sk->sk_filter)) {
 		if (udp_lib_checksum_complete(skb))
-			goto drop;
+			goto csum_error;
 	}
 
 	if (sk_rcvqueues_full(sk, skb, sk->sk_rcvbuf))
···
 	bh_unlock_sock(sk);
 
 	return rc;
+csum_error:
+	UDP6_INC_STATS_BH(sock_net(sk), UDP_MIB_CSUMERRORS, is_udplite);
 drop:
 	UDP6_INC_STATS_BH(sock_net(sk), UDP_MIB_INERRORS, is_udplite);
 	atomic_inc(&sk->sk_drops);
···
 	}
 
 	if (udp6_csum_init(skb, uh, proto))
-		goto discard;
+		goto csum_error;
 
 	/*
 	 *	Multicast receive code
···
 		goto discard;
 
 	if (udp_lib_checksum_complete(skb))
-		goto discard;
+		goto csum_error;
 
 	UDP6_INC_STATS_BH(net, UDP_MIB_NOPORTS, proto == IPPROTO_UDPLITE);
 	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
···
 		       skb->len,
 		       daddr,
 		       ntohs(uh->dest));
-
+	goto discard;
+csum_error:
+	UDP6_INC_STATS_BH(net, UDP_MIB_CSUMERRORS, proto == IPPROTO_UDPLITE);
 discard:
 	UDP6_INC_STATS_BH(net, UDP_MIB_INERRORS, proto == IPPROTO_UDPLITE);
 	kfree_skb(skb);