On Thu, Jan 31, 2019 at 12:01:26PM +0000, YASIN CANER wrote: No idea, what might be wrong with you conf. But you might start by making a packetdump (of all traffic except eg ssh on all interfaces) to see if the problem is related to kamailio or some network related config on the machine.

Hello, I found the problem. it is about Kamailio-master. When i test on 5.2 version, it can relay tcp sip request to other side. I think it is a bug for tcp connection. Thanks. UAC:IPv6:TCP ---> Kamailio (5.2):IPv6:TCP ---> Kamailio:IPv6:TCP (works) ________________________________ From: sr-users &lt;sr-users-bounces(a)lists.kamailio.org&gt; on behalf of YASIN CANER &lt;caner_yaso(a)hotmail.com&gt; Sent: Thursday, January 31, 2019 3:01 PM To: Kamailio (SER) - Users Mailing List Subject: [SR-Users] ERROR : EAGAIN and write queue full or failed for tcp Connection Hello, Kamailio gave this error that couldnt bind tcp connection other side. Thanks Yasin CANER Kamailio IPv6:TCP: -----> IPv6:TCP Kamailio -----> X ERROR XXXX IPv6:TCP Kamailio IPv6::C IPv6::8 IPv6::5 LOGS: 7(15781) DEBUG: <core> [core/msg_translator.c:2937]: create_via_hf(): id added: <;i=1>, rcv proto=2 7(15781) DEBUG: <core> [core/msg_translator.c:162]: check_via_address(): (FD61:C23C:B3B6:0:0:0:0:C, [FD61:C23C:B3B6:0:0:0:0:C], 0) 7(15781) DEBUG: <core> [core/tcp_main.c:1977]: tcp_send(): no open tcp connection found, opening new one 7(15781) DEBUG: <core> [core/ip_addr.c:242]: print_ip(): tcpconn_new: new tcp connection: fd61:c23c:b3b6:0:0:0:0:5 7(15781) DEBUG: <core> [core/tcp_main.c:1229]: tcpconn_new(): on port 5060, type 2 7(15781) DEBUG: <core> [core/tcp_main.c:1539]: tcpconn_add(): hashes: 507:2382:0, 2 7(15781) DEBUG: <core> [core/tcp_main.c:2873]: tcpconn_1st_send(): pending write on new connection 0x7fd15b5e7c98 (-1/1483 bytes written) (err: 11 - Resource temporarily unavailable) 7(15781) ERROR: <core> [core/tcp_main.c:2891]: tcpconn_1st_send(): [FD61:C23C:B3B6:0:0:0:0:5]:5060: EAGAIN and write queue full or failed for 0x7fd15b5e7c98 7(15781) DEBUG: <core> [core/tcp_main.c:3153]: tcpconn_chld_put(): destroying connection 0x7fd15b5e7c98 (2, -1) flags 0060 7(15781) ERROR: tm [../../core/forward.h:251]: msg_send_buffer(): tcp_send failed 7(15781) DEBUG: tm [t_fwd.c:1549]: t_send_branch(): send to FD61:C23C:B3B6:0:0:0:0:5:5060 (2) failed 7(15781) WARNING: tm [t_fwd.c:1567]: t_send_branch(): sending request on branch 0 failed CONF: dns_try_ipv6=yes dns_retr_time=1 dns_retr_no=1 dns_cache_flags=4 tcp_source_ipv6 = [fd61:c23c:b3b6::8] tcp_async=yes tcp_rd_buf_size=65536 tcp_wq_blk_size=3000 listen=tcp:[fd61:c23c:b3b6::8]:5060 tcp_connection_lifetime=3605 listen=tcp:[fd61:c23c:b3b6::8]:5060 ..... route[]{ remove_hf("Route"); #loose_route(); if (!is_method("INVITE")) return; $du="sip: mykamailio1.test:5060;transport=tcp"; if(!t_newtran()){ xlog("L_WARN"," Couldnt create new transaction \r\n"); sl_send_reply("503", "Service not available"); exit; } if(!t_relay()){ send_reply("503", "Service not available"); exit; } exit; }