Freeswitch having DNS Error post systemd-resolved.service restarts

[bhavinmoradiya447]

We're experiencing an issue with one of our production FreeSwitch servers where:

• The server suddenly began responding with 503 NORMAL_TEMPORARY_FAILURE when receiving originate commands
• This behavior started unexpectedly on a previously functioning system
• We use external gateways with proxy parameters set to DNS SRV records

Troubleshooting Steps:

1. Initially, debug logs weren't enabled when the issue occurred
2. After enabling debug logging and manually testing, we discovered FreeSwitch was using 127.0.0.1:53 for DNS resolution
3. This IP is incorrect - our /etc/resolv.conf specifies different nameservers
4. After restarting FreeSwitch, the service began working correctly again, using the nameservers specified in /etc/resolv.conf

Root Cause Investigation:

We found that when the issue started, the apt-daily-upgrade script had run simultaneously, which:

• Updated /etc/resolv.conf with the same nameserver entries (not 127.0.0.1)
• Restarted the systemd-resolved.service

Questions:

1. Why did FreeSwitch begin using 127.0.0.1:53 instead of the nameservers configured in /etc/resolv.conf? Is this a known bug?

2. Once FreeSwitch started using 127.0.0.1:53, it continued using this incorrect nameserver for over 24 hours despite the correct configuration in /etc/resolv.conf. Is this expected behavior? How long does FreeSwitch cache nameserver information?

FreeSwitch version: 1.10.12

OS:
No LSB modules are available.
Distributor ID: Debian
Description: Debian GNU/Linux 12 (bookworm)
Release: 12
Codename: bookworm

Logs: ( DNS host is masked on logs)

2025-09-17 09:26:29.967457 94.50% [NOTICE] switch_channel.c:1142 New Channel sofia/external/+140xxxxxx001 [9c5c83d7-8fcc-4f0d-9fe0-9af4fc3f19d6] nua_common.c:108 nh_create_handle() nua: nh_create_handle: entering nua.c:341 nua_handle_bind() nua: nua_handle_bind: entering 2025-09-17 09:26:29.967457 94.50% [INFO] sofia_glue.c:1659 sofia/external/+140xxxxxx001 sending invite call-id: 9c5c83d7-8fcc-4f0d-9fe0-9af4fc3f19d6 nua.c:632 nua_invite() nua: nua_invite: entering nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_invite nua_params.c:486 nua_stack_set_params() nua: nua_stack_set_params: entering soa.c:278 soa_clone() soa_clone(static::0xffff78001f20, 0xffff78001710, 0xffff8c0b7910) called soa.c:402 soa_set_params() soa_set_params(static::0xffff78080410, ...) called soa.c:402 soa_set_params() soa_set_params(static::0xffff78080410, ...) called soa.c:1051 soa_set_user_sdp() soa_set_user_sdp(static::0xffff78080410, (nil), 0xffff8c0bba48, -1) called soa.c:889 soa_set_capability_sdp() soa_set_capability_sdp(static::0xffff78080410, (nil), 0xffff8c0bba48, -1) called nua_dialog.c:338 nua_dialog_usage_add() nua(0xffff8c0b7910): adding session usage nta.c:4508 nta_leg_tcreate() nta_leg_tcreate(0xffff780909c0) soa.c:1301 soa_init_offer_answer() soa_init_offer_answer(static::0xffff78080410) called soa.c:1425 soa_generate_offer() soa_generate_offer(static::0xffff78080410, 0) called soa_static.c:1147 offer_answer_step() soa_static_offer_answer_action(0xffff78080410, soa_generate_offer): called soa_static.c:1188 offer_answer_step() soa_static(0xffff78080410, soa_generate_offer): generating local description soa_static.c:1216 offer_answer_step() soa_static(0xffff78080410, soa_generate_offer): upgrade with local description soa_static.c:1028 soa_sdp_mode_set() soa_sdp_mode_set(0xffff9c5e4128, (nil), ""): called soa_static.c:1445 offer_answer_step() soa_static(0xffff78080410, soa_generate_offer): storing local description soa.c:1268 soa_get_local_sdp() soa_get_local_sdp(static::0xffff78080410, [(nil)], [0xffff9c5e62d0], [0xffff9c5e62cc]) called nta.c:2727 nta_tpn_by_url() nta: selecting scheme sip sres_cache.c:271 sres_cache_get() sres_cache_get(0xffff78003640, NAPTR, "xx.xxxx.xxxx.net.") called nta.c:10575 outgoing_query_naptr() nta: for "xx.xxxx.xxxx.net" query "xx.xxxx.xxxx.net" NAPTR sres.c:979 sres_query() sres_query(0xffff78003360, 0xffff78026c20, NAPTR, "xx.xxxx.xxxx.net") called sres.c:2742 sres_send_dns_query() sres_send_dns_query(0xffff78003360, 0xffff78019990) called sres.c:2827 sres_send_dns_query() sres_send_dns_query(0xffff78003360, 0xffff78019990) id=63743 NAPTR xx.xxxx.xxxx.net (to [127.0.0.1]:53) nua_session.c:4144 signal_call_state_change() nua(0xffff8c0b7910): call state changed: init -> calling, sent offer soa.c:1268 soa_get_local_sdp() soa_get_local_sdp(static::0xffff78080410, [0xffff9c5e62a0], [0xffff9c5e62a8], [(nil)]) called nua_stack.c:299 nua_stack_event() nua(0xffff8c0b7910): event i_state INVITE sent sres.c:3271 sres_resolver_error() sres_resolver_error(0xffff78003360, 65) called sres.c:3425 sres_resolver_report_error() sres: network error 111 (Connection refused) from 127.0.0.1 by icmp type=3 code=3 reported by 127.0.0.1 sres.c:3071 sres_resend_dns_query() sres_resend_dns_query(0xffff78003360, 0xffff78019990, error) called sres.c:2996 sres_query_report_error() sres(q=0xffff78019990): reporting error NETWORK_ERR for NAPTR xx.xxxx.xxxx.net sres_cache.c:271 sres_cache_get() sres_cache_get(0xffff78003640, SRV, "_sip._udp.xx.xxxx.xxxx.net.") called nta.c:10776 outgoing_query_srv() nta: for "xx.xxxx.xxxx.net" query "_sip._udp.xx.xxxx.xxxx.net" SRV sres.c:979 sres_query() sres_query(0xffff78003360, 0xffff78026c20, SRV, "_sip._udp.xx.xxxx.xxxx.net") called sres.c:2742 sres_send_dns_query() sres_send_dns_query(0xffff78003360, 0xffff901f7a00) called sres.c:2827 sres_send_dns_query() sres_send_dns_query(0xffff78003360, 0xffff901f7a00) id=63744 SRV _sip._udp.xx.xxxx.xxxx.net (to [127.0.0.1]:53) sres.c:3071 sres_resend_dns_query() sres_resend_dns_query(0xffff78003360, 0xffff901f7a00, error) called sres.c:2996 sres_query_report_error() sres(q=0xffff901f7a00): reporting error NETWORK_ERR for SRV _sip._udp.xx.xxxx.xxxx.net sres_cache.c:271 sres_cache_get() sres_cache_get(0xffff78003640, A, "xx.xxxx.xxxx.net.") called nta.c:10987 outgoing_query_a() nta: for "xx.xxxx.xxxx.net" query "xx.xxxx.xxxx.net" A sres.c:979 sres_query() sres_query(0xffff78003360, 0xffff78026c20, A, "xx.xxxx.xxxx.net") called sres.c:2742 sres_send_dns_query() sres_send_dns_query(0xffff78003360, 0xffff78019990) called sres.c:2820 sres_send_dns_query() sres_send_dns_query(): sendto: Connection refused nta.c:1382 set_timeout() nta: timer set to 3200 ms nua_stack.c:301 nua_stack_event() nua(0xffff8c0b7910): event r_invite 503 DNS Error nua_session.c:4144 signal_call_state_change() nua(0xffff8c0b7910): call state changed: calling -> init nua_stack.c:301 nua_stack_event() nua(0xffff8c0b7910): event i_state 503 DNS Error nua_stack.c:301 nua_stack_event() nua(0xffff8c0b7910): event i_terminated 503 DNS Error nua_dialog.c:397 nua_dialog_usage_remove_at() nua(0xffff8c0b7910): removing session usage soa.c:355 soa_destroy() soa_destroy(static::0xffff78080410) called nta.c:4561 nta_leg_destroy() nta_leg_destroy(0xffff780909c0) sres.c:3271 sres_resolver_error() sres_resolver_error(0xffff78003360, 65) called sres.c:3425 sres_resolver_report_error() sres: network error 111 (Connection refused) from 127.0.0.1 by icmp type=3 code=3 reported by 127.0.0.1 nua_stack.c:389 nua_application_event() nua: nua_application_event: entering nua.c:1170 nua_handle_unref_user() nua nua_handle_unref_user(0xffff8c0b7910): entering nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_handle_unref nua.c:1157 nua_unref_user() nua: nua_unref_user: entering nua_stack.c:558 nua_signal() nua((nil)): sent signal r_unref nua_stack.c:389 nua_application_event() nua: nua_application_event: entering nua.c:1170 nua_handle_unref_user() nua nua_handle_unref_user(0xffff8c0b7910): entering nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_handle_unref nua.c:1157 nua_unref_user() nua: nua_unref_user: entering nua_stack.c:558 nua_signal() nua((nil)): sent signal r_unref nua_stack.c:389 nua_application_event() nua: nua_application_event: entering nua.c:1170 nua_handle_unref_user() nua nua_handle_unref_user(0xffff8c0b7910): entering nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_handle_unref nua.c:1157 nua_unref_user() nua: nua_unref_user: entering nua_stack.c:558 nua_signal() nua((nil)): sent signal r_unref nua_stack.c:389 nua_application_event() nua: nua_application_event: entering nua.c:1170 nua_handle_unref_user() nua nua_handle_unref_user(0xffff8c0b7910): entering nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_handle_unref nua.c:1157 nua_unref_user() nua: nua_unref_user: entering nua_stack.c:558 nua_signal() nua((nil)): sent signal r_unref nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_handle_unref nua_stack.c:599 nua_stack_signal() nua((nil)): recv signal r_unref nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_handle_unref nua_stack.c:599 nua_stack_signal() nua((nil)): recv signal r_unref nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_handle_unref nua_stack.c:599 nua_stack_signal() nua((nil)): recv signal r_unref nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_handle_unref nua_stack.c:599 nua_stack_signal() nua((nil)): recv signal r_unref nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_invite nua.c:365 nua_handle_magic() nua: nua_handle_magic: entering nua.c:365 nua_handle_magic() nua: nua_handle_magic: entering nua.c:1170 nua_handle_unref_user() nua nua_handle_unref_user(0xffff8c0b7910): entering nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_handle_unref nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_handle_unref nua.c:1157 nua_unref_user() nua: nua_unref_user: entering nua_stack.c:599 nua_stack_signal() nua((nil)): recv signal r_unref nua_stack.c:558 nua_signal() nua((nil)): sent signal r_unref nua.c:365 nua_handle_magic() nua: nua_handle_magic: entering nua.c:365 nua_handle_magic() nua: nua_handle_magic: entering nua.c:1170 nua_handle_unref_user() nua nua_handle_unref_user(0xffff8c0b7910): entering nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_handle_unref nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_handle_unref nua.c:1157 nua_unref_user() nua: nua_unref_user: entering nua_stack.c:599 nua_stack_signal() nua((nil)): recv signal r_unref nua_stack.c:558 nua_signal() nua((nil)): sent signal r_unref nua.c:365 nua_handle_magic() nua: nua_handle_magic: entering 2025-09-17 09:26:29.967457 94.50% [NOTICE] sofia.c:8769 Hangup sofia/external/+140xxxxxx001 [CS_ROUTING] [NORMAL_TEMPORARY_FAILURE] nua.c:341 nua_handle_bind() nua: nua_handle_bind: entering nua.c:920 nua_handle_destroy() nua: nua_handle_destroy: entering nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_destroy nta.c:4561 nta_leg_destroy() nta_leg_destroy((nil)) nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_destroy nua.c:365 nua_handle_magic() nua: nua_handle_magic: entering nua.c:341 nua_handle_bind() nua: nua_handle_bind: entering nua.c:920 nua_handle_destroy() nua: nua_handle_destroy: entering nua.c:1170 nua_handle_unref_user() nua nua_handle_unref_user(0xffff8c0b7910): entering nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_handle_unref nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_handle_unref nua.c:1157 nua_unref_user() nua: nua_unref_user: entering nua_stack.c:599 nua_stack_signal() nua((nil)): recv signal r_unref nua_stack.c:558 nua_signal() nua((nil)): sent signal r_unref nua.c:365 nua_handle_magic() nua: nua_handle_magic: entering nua.c:365 nua_handle_magic() nua: nua_handle_magic: entering nua.c:920 nua_handle_destroy() nua: nua_handle_destroy: entering nua.c:1170 nua_handle_unref_user() nua nua_handle_unref_user(0xffff8c0b7910): entering nua_stack.c:599 nua_stack_signal() nua(0xffff8c0b7910): recv signal r_handle_unref nua_stack.c:558 nua_signal() nua(0xffff8c0b7910): sent signal r_handle_unref nua.c:1157 nua_unref_user() nua: nua_unref_user: entering nua_stack.c:599 nua_stack_signal() nua((nil)): recv signal r_unref nua_stack.c:558 nua_signal() nua((nil)): sent signal r_unref 2025-09-17 09:26:29.967457 94.50% [NOTICE] switch_core_session.c:1765 Session 14 (sofia/external/+140xxxxxx001) Ended 2025-09-17 09:26:29.967457 94.50% [NOTICE] switch_core_session.c:1769 Close Channel sofia/external/+140xxxxxx001 [CS_DESTROY]