udp: Fix the SNMP counter of UDP_MIB_INDATAGRAMS

If UDP echo is sent to xinetd/echo-dgram, the UDP reply will be received
at the sender. But the SNMP counter of UDP_MIB_INDATAGRAMS will be not
increased, UDP6_MIB_INDATAGRAMS will be increased instead.

  Endpoint A                      Endpoint B
  UDP Echo request ----------->
  (IPv4, Dst port=7)
                   <----------    UDP Echo Reply
                                  (IPv4, Src port=7)

This bug is come from this patch cb75994ec311b2cd50e5205efdcc0696abd6675d.

It do counter UDP[6]_MIB_INDATAGRAMS until udp[v6]_recvmsg. Because
xinetd used IPv6 socket to receive UDP messages, thus, when received
UDP packet, the UDP6_MIB_INDATAGRAMS will be increased in function
udpv6_recvmsg() even if the packet is a IPv4 UDP packet.

This patch fixed the problem.

Signed-off-by: Wei Yongjun <yjwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 5 deletions

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 71e259e866a1..18696af106d6 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -138,6 +138,7 @@ int udpv6_recvmsg(struct kiocb *iocb, struct sock *sk,
         int peeked;
         int err;
         int is_udplite = IS_UDPLITE(sk);
+        int is_udp4;
 
         if (addr_len)
                 *addr_len=sizeof(struct sockaddr_in6);
@@ -158,6 +159,8 @@ try_again:
         else if (copied < ulen)
                 msg->msg_flags |= MSG_TRUNC;
 
+        is_udp4 = (skb->protocol == htons(ETH_P_IP));
+
         /*
          * If checksum is needed at all, try to do it while copying the
          * data.  If the data is truncated, or if we only want a partial
@@ -180,9 +183,14 @@ try_again:
         if (err)
                 goto out_free;
 
-        if (!peeked)
-                UDP6_INC_STATS_USER(sock_net(sk),
-                                UDP_MIB_INDATAGRAMS, is_udplite);
+        if (!peeked) {
+                if (is_udp4)
+                        UDP_INC_STATS_USER(sock_net(sk),
+                                        UDP_MIB_INDATAGRAMS, is_udplite);
+                else
+                        UDP6_INC_STATS_USER(sock_net(sk),
+                                        UDP_MIB_INDATAGRAMS, is_udplite);
+        }
 
         sock_recv_timestamp(msg, sk, skb);
 
@@ -196,7 +204,7 @@ try_again:
                 sin6->sin6_flowinfo = 0;
                 sin6->sin6_scope_id = 0;
 
-                if (skb->protocol == htons(ETH_P_IP))
+                if (is_udp4)
                         ipv6_addr_set(&sin6->sin6_addr, 0, 0,
                                       htonl(0xffff), ip_hdr(skb)->saddr);
                 else {
@@ -207,7 +215,7 @@ try_again:
                 }
 
         }
-        if (skb->protocol == htons(ETH_P_IP)) {
+        if (is_udp4) {
                 if (inet->cmsg_flags)
                         ip_cmsg_recv(msg, skb);
         } else {