snmptrap under IPv6 after setting clientaddr

[Rizwan A. <ra...@mv...>]

Hi all,

Under IPv6 environment, sent snmptrap after setting clientaddr in
snmp.conf, It is sent from another interface.

Test Details..

[root@cghvhp1 ~]# cat /etc/snmp/snmp.conf
clientaddr 2001:ccc1::2
[root@cghvhp1 ~]#

[root@cghvhp1 snmp]# ifconfig eth3
eth3      Link encap:Ethernet  HWaddr 2C:44:FD:7D:D8:F1
          inet addr:192.168.110.1  Bcast:192.168.255.255  Mask:255.255.0.0
          inet6 addr: 2001:ccc1::1/0 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5342 errors:0 dropped:13 overruns:0 frame:0
          TX packets:130 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:693454 (677.2 KiB)  TX bytes:15878 (15.5 KiB)
          Interrupt:36

[root@cghvhp1 snmp]# ifconfig eth4
eth4      Link encap:Ethernet  HWaddr 2C:44:FD:7D:D8:F2
          inet addr:192.168.110.2  Bcast:192.168.255.255  Mask:255.255.0.0
          inet6 addr: 2001:ccc1::2/0 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:21 errors:0 dropped:0 overruns:0 frame:0
          TX packets:38 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2874 (2.8 KiB)  TX bytes:5946 (5.8 KiB)
          Interrupt:32

[root@cghvhp1 snmp]#


snmptrap is sent from eth3 while clientaddr is set to eth4.


I looked into IPv4 code and feel like same code is missing under IPv6
section.

Sending missing code section from IPv6 in
*snmplib/transports/snmpUDPIPv6Domain.c*

diff --git a/snmplib/transports/snmpUDPIPv6Domain.c
b/snmplib/transports/snmpUDPIPv6Domain.c
index b3eaae4..85a2f7a 100644
--- a/snmplib/transports/snmpUDPIPv6Domain.c
+++ b/snmplib/transports/snmpUDPIPv6Domain.c
@@ -190,6 +190,7 @@ netsnmp_udp6_transport(struct sockaddr_in6 *addr, int
local)
 {
     netsnmp_transport *t = NULL;
     int             rc = 0;
+    char           *client_socket = NULL;

 #ifdef NETSNMP_NO_LISTEN_SUPPORT
     if (local)
@@ -267,10 +268,29 @@ netsnmp_udp6_transport(struct sockaddr_in6 *addr, int
local)
 #endif /* NETSNMP_NO_LISTEN_SUPPORT */
     } else {
         /*
+         * This is a client session.  If we've been given a
+         * client address to send from, then bind to that.
+         * Otherwise the send will use "something sensible".
+         */
+        client_socket = netsnmp_ds_get_string(NETSNMP_DS_LIBRARY_ID,
+                                              NETSNMP_DS_LIB_CLIENT_ADDR);
+        if (client_socket) {
+            struct sockaddr_in6 client_addr;
+            netsnmp_sockaddr_in6_2(&client_addr, client_socket, NULL);
+            rc = bind(t->sock, (struct sockaddr *)&client_addr,
+                  sizeof(struct sockaddr_in6));
+            if ( rc != 0 ) {
+                DEBUGMSGTL(("netsnmp_udp6", "failed to bind for
clientaddr: %d %s\n",
+                            errno, strerror(errno)));
+                netsnmp_socketbase_close(t);
+                netsnmp_transport_free(t);
+            }
+        }
+        /*
          * This is a client session.  Save the address in the
          * transport-specific data pointer for later use by
netsnmp_udp6_send.
          */
-
         t->data = malloc(sizeof(netsnmp_indexed_addr_pair));
         if (t->data == NULL) {
             netsnmp_socketbase_close(t);



I need to confirm the changes, This is required to send snmptrap after
setting clientaddr in snmp.conf.

Please provide your  feedback regarding this change.


Thanks,
Rizwan