[switch_core_media] RFC 2543-style hold not detected for IPv6 endpoints — HELD state never triggered - #3099
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… multi-node use, but the implementation was never completed. All SQL writers hardcode the literal string 'single_box' instead of reading a configurable value from the module's global configuration.
…inate leg via ovars
…umber on Polycom endpoints
…r RFC 2543 SDP hold
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I agree that this seems like an oversight. We have had to custom-code around this. |
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Description
reeSWITCH detects RFC 2543-style call hold by checking whether the SDP's connection address (c= line) is set to the IPv4 null address 0.0.0.0. This detection is in switch_core_media_process_sdp() in src/switch_core_media.c.
However, the check does not include the equivalent IPv6 null address 0:0:0:0:0:0:0:0 (or its canonical form ::). IPv6-capable endpoints — notably Cisco IP phones in dual-stack environments — send RFC 2543-style hold using the IPv6 null address in the SDP connection line. FreeSWITCH does not recognize this as a hold, so the channel never transitions to the HELD state, breaking all hold-dependent features: music on hold, hold timers, supervisor monitoring, and hold/resume event generation.
RFC Reference
RFC 2543 §3.1 specifies that a hold is signaled by setting the SDP connection address to 0.0.0.0. RFC 3264 deprecated this in favor of a=sendonly/recvonly, but many deployed devices (especially Cisco) continue to use RFC 2543-style hold. For IPv6, the equivalent address is 0:0:0:0:0:0:0:0 (abbreviated ::). FreeSWITCH already handles the IPv4 case; the IPv6 case is missing.
Affected Code
File: src/switch_core_media.c
Function: switch_core_media_process_sdp() — the sdp_connection->c_address check approximately 124 lines before the main media loop.
Type of Change
Related Issues
#3098 (comment)
Testing
(1) Configure FreeSWITCH with an IPv6-enabled sofia profile (listen-ip = ::).
(2) Register a Cisco IP phone (e.g., Cisco 8800 series) that sends RFC 2543-style hold via IPv6.
(3) Place a call to/from the Cisco phone. While connected, press the Hold button on the phone.
(4) Capture the re-INVITE or UPDATE sent by the phone using sofia global siptrace on.
(5) Observe the SDP contains c=IN IP6 0:0:0:0:0:0:0:0 in the connection field.
(6) Check the channel state:
fs_cli -x "show channels"
or monitor SWITCH_EVENT_CHANNEL_HOLD — the channel does NOT enter the HELD state.
(7) Music on hold is not triggered; the far end hears live audio (or silence) instead of MOH.
Checklist
Additional Notes