Is the underlying UDP socket non-blocking in linux?

[gou4shi1]

Found that sometimes the send queue may be too slow:

14:27:21.141148 /SRT:SndQ:w2 D:SRT.qs: CSndQueue: requesting packet from @572158503 STATUS: -Listening -Connecting +Connected -Closing -Shutdown -Broken +PeerHealth +Opened 
14:27:21.141236 /SRT:SndQ:w2 D:SRT.qs: chn:SENDING: TARGET=@695743876 DATA: size=1144 00C400CC #125 %1676856765 PB_SOLO ORD_RELAXED EK_NOENC SN_ORIGINAL
14:27:21.171997 /remote_interfac D:SRT.bs: addBuffer: size=10 reserved=32 needs=1 buffers for 1320 bytes
14:27:21.172003 /remote_interfac D:SRT.bs: addBuffer: adding 1 packets (1320 bytes) to send, msgno=136 NOT in order
14:27:21.172007 /remote_interfac D:SRT.bs: addBuffer: using internally managed msgno=136
14:27:21.172013 /remote_interfac D:SRT.bs: addBuffer: %1676856776 #136 spreading from=0 size=1320 TO BUFFER:0x7f6e5c004e20
14:27:21.172022 /remote_interfac D:SRT.bs: CSndBuffer::addBuffer: updating msgno: #136 -> #137
14:27:21.172051 /remote_interfac D:SRT.bs: addBuffer: size=11 reserved=32 needs=1 buffers for 1320 bytes
14:27:21.172054 /remote_interfac D:SRT.bs: addBuffer: adding 1 packets (1320 bytes) to send, msgno=136 NOT in order
14:27:21.172057 /remote_interfac D:SRT.bs: addBuffer: OVERWRITTEN by msgno supplied by caller: msgno=136
14:27:21.172060 /remote_interfac D:SRT.bs: addBuffer: %1676856776 #136 spreading from=0 size=1320 TO BUFFER:0x7f6e600043e0
14:27:21.172066 /remote_interfac D:SRT.bs: CSndBuffer::addBuffer: updating msgno: #136 -> #137
14:27:21.275641 /remote_interfac D:SRT.bs: addBuffer: size=11 reserved=32 needs=1 buffers for 1240 bytes
14:27:21.275645 /remote_interfac D:SRT.bs: addBuffer: adding 1 packets (1240 bytes) to send, msgno=137 NOT in order
14:27:21.275648 /remote_interfac D:SRT.bs: addBuffer: using internally managed msgno=137
14:27:21.275652 /remote_interfac D:SRT.bs: addBuffer: %1676856777 #137 spreading from=0 size=1240 TO BUFFER:0x7f6e5c0053c8
14:27:21.275656 /remote_interfac D:SRT.bs: CSndBuffer::addBuffer: updating msgno: #137 -> #138
14:27:21.275724 /remote_interfac D:SRT.bs: addBuffer: size=11 reserved=32 needs=1 buffers for 1240 bytes
14:27:21.275743 /remote_interfac D:SRT.bs: addBuffer: adding 1 packets (1240 bytes) to send, msgno=137 NOT in order
14:27:21.275752 /remote_interfac D:SRT.bs: addBuffer: OVERWRITTEN by msgno supplied by caller: msgno=137
14:27:21.275758 /remote_interfac D:SRT.bs: addBuffer: %1676856777 #137 spreading from=0 size=1240 TO BUFFER:0x7f6e60004988
14:27:21.275767 /remote_interfac D:SRT.bs: CSndBuffer::addBuffer: updating msgno: #137 -> #138
14:27:21.317822 /SRT:SndQ:w1 D:SRT.qs: CSndQueue: requesting packet from @572158504 STATUS: -Listening -Connecting +Connected -Closing -Shutdown -Broken +PeerHealth +Opened 
14:27:21.317903 /SRT:SndQ:w1 D:SRT.qs: chn:SENDING: TARGET=@695743874 DATA: size=1232 00C800CC #127 %1676856767 PB_SOLO ORD_RELAXED EK_NOENC SN_ORIGINAL
14:27:21.349185 /SRT:SndQ:w2 D:SRT.qs: CSndQueue: requesting packet from @572158503 STATUS: -Listening -Connecting +Connected -Closing -Shutdown -Broken +PeerHealth +Opened 
14:27:21.349266 /SRT:SndQ:w2 D:SRT.qs: chn:SENDING: TARGET=@695743876 DATA: size=1144 00C400CC #126 %1676856766 PB_SOLO ORD_RELAXED EK_NOENC SN_ORIGINAL

Is it stuck at sendmsg() or waitNonEmpty()?

[gou4shi1]

    // Set non-blocking I/O
    // UNIX does not support SO_RCVTIMEO
    int opts = ::fcntl(m_iSocket, F_GETFL);
    if (-1 == ::fcntl(m_iSocket, F_SETFL, opts | O_NONBLOCK))
        throw CUDTException(MJ_SETUP, MN_NORES, NET_ERROR);

seems that it's non-blocking

[maxsharabayko]

Yes, it is non-blocking.

[gou4shi1]

Maybe CUDT::checkNeedDrop() should also check TTL in message mode?