Hello,

I'm wondering why kamailio will try doing a DNS lookup of the from host with a REGISTER packet when using TCP?
It doesn't do this with UDP.

I always get this error since the host is not a valid domain:

<core> [resolve.c:1726]: sip_hostport2su(): could not resolve hostname: "3.local"

Here is the full log with debug (error is last line)

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: <core> [mem/shm_mem.c:111]: _shm_resize(): WARNING:vqm_resize: resize(0) called

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: <core> [tcp_main.c:2294]: tcpconn_send_put(): tcp_send: found fd in cache ( 10, 0x7f860bd18938, 1)

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: <core> [tcp_main.c:2516]: tcpconn_do_send(): tcp_send: sending...

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: <core> [tcp_main.c:2550]: tcpconn_do_send(): tcp_send: after real write: c= 0x7f860bd18938 n=639 fd=10

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: <core> [tcp_main.c:2551]: tcpconn_do_send(): tcp_send: buf=#012SIP/2.0 401 Unauthorized#015#012Via: SIP/2.0/TCP 192.168.16.120:53972;received=192.168.213.162;rport=53972;branch=z9hG4bKPjac894585917043d28da015d397178725;alias#015#012From: "1003" <sip:1003@3.local>;tag=dbc7a9087cb84006b65d891e5ad1f5ea#015#012To: "1003" <sip:1003@3.local>;tag=ey7D0K9DX49DF#015#012Call-ID: ee72194a1b8e4effa2948e237d804b90#015#012CSeq: 1 REGISTER#015#012User-Agent: AMPSwitch#015#012Allow: INVITE, ACK, BYE, CANCEL, OPTIONS, MESSAGE, INFO, UPDATE, REGISTER, REFER, NOTIFY, PUBLISH, SUBSCRIBE#015#012Supported: timer, path, replaces#015#012WWW-Authenticate: Digest realm="3.local", nonce="cdf32dde-ab14-4265-b491-bee703e83255", algorithm=MD5, qop="auth"#015#012Content-Length: 0#015#012#015#012

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: tm [t_reply.c:1663]: cleanup_uac_timers(): DEBUG: cleanup_uac_timers: RETR/FR timers reset

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: <core> [usr_avp.c:643]: destroy_avp_list(): DEBUG:destroy_avp_list: destroying list (nil)

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: <core> [xavp.c:448]: xavp_destroy_list(): destroying xavp list (nil)

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: <core> [receive.c:298]: receive_msg(): receive_msg: cleaning up

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3026]: DEBUG: <core> [io_wait.h:388]: io_watch_add(): DBG: io_watch_add(0xa2c420, 6, 2, 0x7f860bd2dbe0), fd_no=1

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/msg_parser.c:629]: parse_msg(): version: <SIP/2.0>

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/parse_via.c:1284]: parse_via_param(): Found param type 235, <rport> = <n/a>; state=6

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/parse_via.c:1284]: parse_via_param(): Found param type 232, <branch> = <z9hG4bKPj19019d19feaa4a06ac1d6cdc31a2e05d>; state=6

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/parse_via.c:1284]: parse_via_param(): Found param type 237, <alias> = <n/a>; state=16

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/parse_via.c:2672]: parse_via(): end of header reached, state=5

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/msg_parser.c:513]: parse_headers(): parse_headers: Via found, flags=2

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/msg_parser.c:515]: parse_headers(): parse_headers: this is the first via

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [receive.c:154]: receive_msg(): After parse_msg...

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [receive.c:197]: receive_msg(): preparing to run routing scripts...

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: maxfwd [mf_funcs.c:85]: is_maxfwd_present(): value = 70

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/parse_addr_spec.c:898]: parse_addr_spec(): end of header reached, state=10

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/msg_parser.c:190]: get_hdr_field(): DEBUG: get_hdr_field: <To> [27]; uri=[sip:1003@3.local]

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/msg_parser.c:192]: get_hdr_field(): DEBUG: to body ["1003" <sip:1003@3.local>#015#012]

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/msg_parser.c:170]: get_hdr_field(): get_hdr_field: cseq <CSeq>: <1> <PUBLISH>

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/msg_parser.c:204]: get_hdr_field(): DEBUG: get_hdr_body : content_length=757

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [parser/msg_parser.c:106]: get_hdr_field(): found end of header

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: sanity [mod_sanity.c:255]: w_sanity_check(): sanity checks result: 1

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: textops [textops.c:2478]: has_body_f(): content type is 196613

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: siputils [checks.c:103]: has_totag(): no totag

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: tm [t_lookup.c:1072]: t_check_msg(): DEBUG: t_check_msg: msg id=10 global id=9 T start=0xffffffffffffffff

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: tm [t_lookup.c:527]: t_lookup_request(): t_lookup_request: start searching: hash=12001, isACK=0

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: tm [t_lookup.c:485]: matching_3261(): DEBUG: RFC3261 transaction matching failed

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: tm [t_lookup.c:709]: t_lookup_request(): DEBUG: t_lookup_request: no transaction found

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: tm [t_lookup.c:1141]: t_check_msg(): DEBUG: t_check_msg: msg id=10 global id=10 T end=(nil)

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: tm [t_lookup.c:1373]: t_newtran(): DEBUG: t_newtran: msg id=10 , global msg id=10 , T on entrance=(nil)

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: tm [t_lookup.c:527]: t_lookup_request(): t_lookup_request: start searching: hash=12001, isACK=0

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: tm [t_lookup.c:485]: matching_3261(): DEBUG: RFC3261 transaction matching failed

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: tm [t_lookup.c:709]: t_lookup_request(): DEBUG: t_lookup_request: no transaction found

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [md5utils.c:67]: MD5StringArray(): DEBUG: MD5 calculated: d71ddc300035dfaa15e181fe4d6a9aa7

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [dns_cache.c:566]: _dns_hash_find(): dns_hash_find(_sip._tcp.3.local(17), 33), h=867

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [resolve.c:770]: get_record(): get_record: lookup(_sip._tcp.3.local, 33) failed

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [dns_cache.c:894]: dns_cache_mk_bad_entry(): dns_cache_mk_bad_entry(_sip._tcp.3.local, 33, 60, 1)

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [dns_cache.c:827]: dns_cache_add(): dns_cache_add: adding _sip._tcp.3.local(17) 33 (flags=1) at 867

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [dns_cache.c:566]: _dns_hash_find(): dns_hash_find(3.local(7), 1), h=184

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [resolve.c:770]: get_record(): get_record: lookup(3.local, 1) failed

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [dns_cache.c:894]: dns_cache_mk_bad_entry(): dns_cache_mk_bad_entry(3.local, 1, 60, 1)

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: DEBUG: <core> [dns_cache.c:827]: dns_cache_add(): dns_cache_add: adding 3.local(7) 1 (flags=1) at 184

Nov 12 15:45:19 ua01-proxy01 /usr/sbin/kamailio[3025]: ERROR: <core> [resolve.c:1726]: sip_hostport2su(): could not resolve hostname: "3.local"