ssl - What happens after TCP ZeroWindow is introduced? -


in client/server communication, seeing tcp zerowindow client.

what expected scenario(what flags set , send) after situation?

below possible logs getting. in case server sends rst packet terminate connection.why has happened?

client(hp ux machine), server (rhel machine)

wireshark dump on server

17:55:03.756500     tcp 62  58304 → 1556 [syn] seq=0 win=32768 len=0 mss=1460 ws=1 17:55:03.756522     tcp 62  1556 → 58304 [syn, ack] seq=0 ack=1 win=14600                      len=0 mss=1460 ws=128 17:55:03.760562     tlsv1.2 571 client hello 17:55:03.760588     tcp 54  1556 → 58304 [ack] seq=1 ack=518 win=15744                      len=0 17:55:03.769564     tcp 1514    1556 → 58304 [ack] seq=1 ack=518 win=15744                      len=1460 [tcp segment of reassembled pdu] 17:55:03.769588     tlsv1.2 618 server hello, certificate, server key                      exchange, certificate request, server hello done 17:55:03.769689     tcp 60  58304 → 1556 [ack] seq=518 ack=1461 win=32768                      len=0 17:55:03.828427     tcp 60  58304 → 1556 [ack] seq=518 ack=2025 win=32768                      len=0 17:55:23.789662     tlsv1.2 61  alert (level: fatal, description: unexpected                      message) 17:55:23.789748     tcp 54  1556 → 58304 [fin, ack] seq=2032 ack=518                      win=15744 len=0 17:55:23.789951     tcp 60  58304 → 1556 [ack] seq=518 ack=2033 win=32768                      len=0 17:55:25.662787     tlsv1.2 192 [tcp zerowindow] , certificate, client key                      exchange, change cipher spec, encrypted handshake                      message 17:55:25.662798     tcp 54  1556 → 58304 [rst] seq=2033 win=0 len=0

client curl logs

info: alpn, offering http/1.1 info: cipher selection:  all:!export:!export40:!export56:!anull:!low:!rc4:@strength info: set certificate verify locations: info: tlsv1.2 (out), tls header, certificate status (22): info: tlsv1.2 (out), tls handshake, client hello (1): info: tlsv1.2 (in), tls handshake, server hello (2): info: tlsv1.2 (in), tls handshake, certificate (11): info: tlsv1.2 (in), tls handshake, server key exchange (12): info: tlsv1.2 (in), tls handshake, request cert (13): info: tlsv1.2 (in), tls handshake, server finished (14): info: tlsv1.2 (out), tls handshake, certificate (11): info: tlsv1.2 (out), tls handshake, client key exchange (16): info: tlsv1.2 (out), tls change cipher, client hello (1): info: tlsv1.2 (out), tls handshake, finished (20): info: tlsv1.2 (in), tls alert, server hello (2): info: error:140943f2:ssl routines:ssl3_read_bytes:sslv3 alert unexpected  message info: closing connection 0

the question expected flow of control when tcp zerowindow occurs , how communication restarted after zerowindow timeout?

below in description of alert packet. not sure un expected.

transmission control protocol,seq: 2025, ack: 518, len: 7  [stream index: 2439] [tcp segment len: 7] sequence number: 2025    (relative sequence number) [next sequence number: 2032    (relative sequence number)] acknowledgment number: 518    (relative ack number) 0101 .... = header length: 20 bytes (5) flags: 0x018 (psh, ack) window size value: 123 [calculated window size: 15744] [window size scaling factor: 128] checksum: 0x9e59 [unverified] [checksum status: unverified] urgent pointer: 0 [seq/ack analysis]     [irtt: 0.004062000 seconds]     [bytes in flight: 7]     [bytes sent since last psh flag: 7] tcp payload (7 bytes) secure sockets layer tlsv1.2 record layer: alert (level: fatal, description: unexpected message)     content type: alert (21)     version: tls 1.2 (0x0303)     length: 2     alert message         level: fatal (2)         description: unexpected message (10)

please let me else information might helpful through.

the peer advertises different window size, possibly in response window probe. 0 window on final rst isn't relevant.

the server has sent fin/ack before final rst. don't overlook it. have sent didn't like, in case client certificate.


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