[SR-Users] How to get $fU and $tU from MSRP module?

Hello! I want to get $fU and $tU from event_route[msrp:frame-in] in order to filter out MSRP messages sent by a specific sender and received by a specific receiver, I know I can get message content from $msrp(buf), the message content is like this: MSRP 7a57f552155926c0 SEND To-Path: msrp://172.18.0.14:6060/9d8da4a34dc2102959e7;tcp msrp://172.18.0.12:5060/msrp-6142fc2b-84-1;tcp msrp://172.18.0.2:34862/2a67b54ae0750b7d82aa;tcp From-Path: msrp://172.18.0.14:6060/c71ae3675e114d08216b;tcp msrp://172.18.0.12:5060/msrp-6142fc2b-83-1;tcp msrp://172.18.0.2:34858/8baea7c52ba8755322fd;tcp Byte-Range: 1-197/197 Failure-Report: yes Success-Report: yes Message-ID: c792c94039b8a969 Content-Type: message/cpim From: sip:alice@ims.mnc001.mcc001.3gppnetwork.org To: sip:bob@ims.mnc001.mcc001.3gppnetwork.org DateTime: 2021-09-16T09:23:49.339805+00:00 MIME-Version: 1.0 Content-Type: text/plain hello -------7a57f552155926c0$ I want to get alice and bob from the content below： From: sip:alice@ims.mnc001.mcc001.3gppnetwork.org To: sip:bob@ims.mnc001.mcc001.3gppnetwork.org DateTime: 2021-09-16T09:23:49.339805+00:00 someone can suggest some method. In other route like request_route we can use $fU and $tU to access them. Regrads HANG LI