Hi
We have found net-snmp 5.4 behaves differently to 5.3.1 with regard to
snmp requests sent to a broadcast IP address. Eg. 192.168.1.255. We are
running linux.
5.3.1 responds no problem; 5.4 sees the request but is unable to send a
response.
This is because in 5.4 in snmplib/snmpUDPDomain.c it tries hard to send
back the request on the local address it was received on. In this case
it is the broadcast address to which the OS returns EINVAL on the
sendmsg call.
The workaround is simply instead of using netsnmp_udp_sendto to send the
packet, which attempts to specify which local address should be used to
send from, to use 'sendto'. This restores the behaviour of 5.3.1
i.e.
#if defined(linux) && defined(IP_PKTINFO)
rc = netsnmp_udp_sendto(t->sock, addr_pair ?
&(addr_pair->local_addr) : NULL, to, buf, size);
#else
rc = sendto(t->sock, buf, size, 0, to, sizeof(struct
sockaddr));
#endif /* linux && IP_PKTINFO */
Becomes
#if 0
rc = netsnmp_udp_sendto(t->sock, addr_pair ?
&(addr_pair->local_addr) : NULL, to, buf, size);
#else
rc = sendto(t->sock, buf, size, 0, to, sizeof(struct
sockaddr));
#endif /* linux && IP_PKTINFO */
Best regards
John Gumb
TANDBERG Telecom UK Ltd
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