snmpv1 trap ipv6, error "unknown host: 2000::1996"

[phongting]

version: net-snmp 5.9.1
When I snmptraped with ipv6 in the agent-addr parameter, snmptrap reported the error: "unknown host: 2000::1996".
/usr/local/net-snmp/bin/snmptrap -v1 -c test [2000::1995]:162 '' 2000::1996 6 0 1000 snmpInSetRequests.0 c 0

If I replace ipv4 with '2000::1996', it would send seccess:
/usr/local/net-snmp/bin/snmptrap -v1 -c test [2000::1995]:162 '' 192.168.1.1 6 0 1000 snmpInSetRequests.0 c 0

Viewing the code, I find snmptrap parsing the arg of agent-addr with function 'netsnmp_gethostbyname_v4()':
apps\snmptrap.c:273

agent = argv[arg];
if (agent != NULL && strlen(agent) != 0) {
    int ret = netsnmp_gethostbyname_v4(agent, pdu_in_addr_t);
    if (ret < 0) {
        fprintf(stderr, "unknown host: %s\n", agent);
        goto out;
    }
} else {
    *pdu_in_addr_t = get_myaddr();
}

[bvanassche]

SNMPv1 traps only support IPv4 agent addresses according to https://datatracker.ietf.org/doc/html/rfc1157.