[SR-Users] Why Kamailio reply with null compression method when TLS handshake?

Hi, all. I has set up a Kamailio server with TLS & compression enabled, I thought I set most things suitable , I has set modparam("tls","tls_disable_compression",0) I can find such log records as below when Kamailio boost: 0(10905) INFO: tls [tls_init.c:549]: init_tls_h(): tls: _init_tls_h: compiled with openssl version "OpenSSL 1.0.0-fips 29 Mar 2010" (0x10000003), kerberos support: on, compression: on 0(10905) INFO: tls [tls_init.c:557]: init_tls_h(): tls: init_tls_h: installed openssl library version "OpenSSL 1.0.0-fips 29 Mar 2010" (0x10000003), kerberos support: on, zlib compression: on compiler: gcc -fPIC -DOPENSSL_PIC -DZLIB -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -DKRB5_MIT -m64 -DL_ENDIAN -DTERMIO -Wall -O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m64 -mtune=generic -Wa,--noexecstack -DMD32_REG_T=int -DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DMD5_ASM -DAES_ASM -DWHIRLPOOL_ASM 0(10905) WARNING: tls [tls_init.c:611]: init_tls_h(): tls: openssl bug #1491 (crash/mem leaks on low memory) workaround enabled (on low memory tls operations will fail preemptively) with free memory thresholds 11534336 and 5767168 bytes 0(10905) INFO: <core> [cfg/cfg_ctx.c:613]: cfg_set_now(): INFO: cfg_set_now(): tls.low_mem_threshold1 has been changed to 11534336 0(10905) INFO: <core> [cfg/cfg_ctx.c:613]: cfg_set_now(): INFO: cfg_set_now(): tls.low_mem_threshold2 has been changed to 5767168 And I run kamcmd tls.options, I got: { force_run: 0 method: TLSv1 verify_certificate: 0 verify_depth: 9 require_certificate: 0 private_key: /ca/cert.pem ca_list: certificate: /ca/cert.pem cipher_list: session_cache: 1 session_id: vic22 config: /etc/kamailio/tls.cfg log: 3 debug: 3 connection_timeout: 600 disable_compression: 0 ssl_release_buffers: -1 ssl_freelist_max: -1 ssl_max_send_fragment: -1 ssl_read_ahead: 0 send_close_notify: 0 low_mem_threshold1: 11534336 low_mem_threshold2: 5767168 ct_wq_max: 10485760 con_ct_wq_max: 65536 ct_wq_blk_size: 4096 } But when My UA connect to this server, when TLS handshake, I can find that the clienthello with two compression method :1 (deflate) and 0 (null), but the server side reply with just one compression method: 0( null), thus the compression was disabled through the following communication. Why? are there any others issue can impact the behavior of Kamailio? Any hints will be appreciated. B.R. Rixin liu