O ISP acabou de entrar em contato comigo. Foi uma falha de configuração dentro de sua rede, o que levou à queda do pacote PASV.
Atualizar O ISP disse que recentemente adicionou a área onde este computador está localizado em sua rede IPv6. Coincidentemente, desde o dia em que eles adicionaram essa área à sua rede IPv6, nenhuma conexão FTP foi possível.
O ISP conseguiu definir essa conexão específica de volta ao IPv4 (por um período limitado) e ... O FTP funcionou novamente.
Descrição original do problema
Eu tenho um problema de nível TCP entre clientes FTP e servidores FTP (acho que é um servidor proftp, mas não tenho certeza).
Ao solicitar o modo PASV para transferência de dados, o cliente recebe um ACK, mas não recebe a mensagem 227 entering passive mode . O cliente aguarda 30 segundos antes de enviar um TYPE A request , que o servidor tenta ACK, mas com o número SEQ errado.
O número SEQ contém o tamanho da mensagem Enter passive mode . O servidor também envia um 200 Switching to ASCII mode que também possui o número SEQ incorreto.
De lá, são 7 tentativas de TCP Retransmission e TCP DUP ACK, enquanto ambos os lados estão usando 'seus' números SEQ. (Não deve a mensagem não confirmada que o servidor enviou ser retransmitido? Significado, não deve o servidor apenas enviou a mensagem 227 entering passive mode novamente? Ou, pelo menos, corrigir o número SEQ?)
Eu tenho várias perguntas aqui. Por um lado, qual lado está se comportando errado aqui? Um lado tem que consertar o seu número SEQ, mas quem? E como uma mensagem específica (sempre é a mensagem Entering passive mode ) sempre se perde?
Para tornar as coisas mais estranhas, isso está acontecendo apenas em um computador. Fora de centenas. E isso também está acontecendo apenas com um servidor FTP. (que eu não tenho controle). O servidor e o computador em questão estão conectados via internet.
Os registros foram adquiridos por meio do roteador do cliente, portanto, não é um problema no computador.
Ok, consegui filtrar o protocolo. Então aqui está:
No. Time Protocol Length Info
39 5.988043 FTP 68 Request: PASV
Frame 39: 68 bytes on wire (544 bits), 68 bytes captured (544 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 68, Ack: 294, Len: 6
File Transfer Protocol (FTP)
No. Time Protocol Length Info
40 6.034184 TCP 62 ftp > 49736 [ACK] Seq=294 Ack=74 Win=32695 Len=0
Frame 40: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 294, Ack: 74, Len: 0
No. Time Protocol Length Info
41 36.381924 FTP 70 Request: TYPE A
Frame 41: 70 bytes on wire (560 bits), 70 bytes captured (560 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 74, Ack: 294, Len: 8
File Transfer Protocol (FTP)
No. Time Protocol Length Info
42 36.417678 TCP 62 [TCP Previous segment lost] ftp > 49736 [ACK] Seq=345 Ack=82 Win=32687 Len=0
Frame 42: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 345, Ack: 82, Len: 0
No. Time Protocol Length Info
43 36.435735 FTP 92 Response: 200 Switching to ASCII mode.
Frame 43: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 345, Ack: 82, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
44 36.436237 TCP 62 [TCP Dup ACK 41#1] 49736 > ftp [ACK] Seq=82 Ack=294 Win=65047 Len=0
Frame 44: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 82, Ack: 294, Len: 0
No. Time Protocol Length Info
45 37.274734 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 45: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 345, Ack: 82, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
46 37.275388 TCP 62 [TCP Dup ACK 41#2] 49736 > ftp [ACK] Seq=82 Ack=294 Win=65047 Len=0
Frame 46: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 82, Ack: 294, Len: 0
No. Time Protocol Length Info
47 38.515559 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 47: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 345, Ack: 82, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
48 38.516182 TCP 62 [TCP Dup ACK 41#3] 49736 > ftp [ACK] Seq=82 Ack=294 Win=65047 Len=0
Frame 48: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 82, Ack: 294, Len: 0
No. Time Protocol Length Info
49 40.376003 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 49: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 345, Ack: 82, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
50 40.376567 TCP 62 [TCP Dup ACK 41#4] 49736 > ftp [ACK] Seq=82 Ack=294 Win=65047 Len=0
Frame 50: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 82, Ack: 294, Len: 0
No. Time Protocol Length Info
51 43.474007 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 51: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 345, Ack: 82, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
52 43.474611 TCP 62 [TCP Dup ACK 41#5] 49736 > ftp [ACK] Seq=82 Ack=294 Win=65047 Len=0
Frame 52: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 82, Ack: 294, Len: 0
No. Time Protocol Length Info
53 49.053924 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 53: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 345, Ack: 82, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
54 49.054515 TCP 62 [TCP Dup ACK 41#6] 49736 > ftp [ACK] Seq=82 Ack=294 Win=65047 Len=0
Frame 54: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 82, Ack: 294, Len: 0
No. Time Protocol Length Info
55 59.593195 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 55: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 345, Ack: 82, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
56 59.593832 TCP 62 [TCP Dup ACK 41#7] 49736 > ftp [ACK] Seq=82 Ack=294 Win=65047 Len=0
Frame 56: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 82, Ack: 294, Len: 0
No. Time Protocol Length Info
57 66.796925 FTP 70 Request: TYPE A
Frame 57: 70 bytes on wire (560 bits), 70 bytes captured (560 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 82, Ack: 294, Len: 8
File Transfer Protocol (FTP)
No. Time Protocol Length Info
58 66.833363 TCP 62 ftp > 49736 [ACK] Seq=375 Ack=90 Win=32679 Len=0
Frame 58: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 375, Ack: 90, Len: 0
No. Time Protocol Length Info
59 66.852889 FTP 92 Response: 200 Switching to ASCII mode.
Frame 59: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 375, Ack: 90, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
60 66.853447 TCP 62 [TCP Dup ACK 57#1] 49736 > ftp [ACK] Seq=90 Ack=294 Win=65047 Len=0
Frame 60: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 90, Ack: 294, Len: 0
No. Time Protocol Length Info
61 67.653089 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 61: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 375, Ack: 90, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
62 67.653593 TCP 62 [TCP Dup ACK 57#2] 49736 > ftp [ACK] Seq=90 Ack=294 Win=65047 Len=0
Frame 62: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 90, Ack: 294, Len: 0
No. Time Protocol Length Info
63 68.894847 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 63: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 375, Ack: 90, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
64 68.895352 TCP 62 [TCP Dup ACK 57#3] 49736 > ftp [ACK] Seq=90 Ack=294 Win=65047 Len=0
Frame 64: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 90, Ack: 294, Len: 0
No. Time Protocol Length Info
65 70.755267 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 65: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 375, Ack: 90, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
66 70.755790 TCP 62 [TCP Dup ACK 57#4] 49736 > ftp [ACK] Seq=90 Ack=294 Win=65047 Len=0
Frame 66: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 90, Ack: 294, Len: 0
No. Time Protocol Length Info
67 73.851892 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 67: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 375, Ack: 90, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
68 73.852389 TCP 62 [TCP Dup ACK 57#5] 49736 > ftp [ACK] Seq=90 Ack=294 Win=65047 Len=0
Frame 68: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 90, Ack: 294, Len: 0
No. Time Protocol Length Info
69 79.432036 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 69: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 375, Ack: 90, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
70 79.432625 TCP 62 [TCP Dup ACK 57#6] 49736 > ftp [ACK] Seq=90 Ack=294 Win=65047 Len=0
Frame 70: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 90, Ack: 294, Len: 0
No. Time Protocol Length Info
71 87.075370 FTP 70 Request: TYPE A
Frame 71: 70 bytes on wire (560 bits), 70 bytes captured (560 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 90, Ack: 294, Len: 8
File Transfer Protocol (FTP)
No. Time Protocol Length Info
72 87.111901 TCP 62 ftp > 49736 [ACK] Seq=405 Ack=98 Win=32671 Len=0
Frame 72: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 405, Ack: 98, Len: 0
No. Time Protocol Length Info
73 87.131366 FTP 92 Response: 200 Switching to ASCII mode.
Frame 73: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 405, Ack: 98, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
74 87.131840 TCP 62 [TCP Dup ACK 71#1] 49736 > ftp [ACK] Seq=98 Ack=294 Win=65047 Len=0
Frame 74: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 98, Ack: 294, Len: 0
No. Time Protocol Length Info
75 87.801062 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 75: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 405, Ack: 98, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
76 87.801573 TCP 62 [TCP Dup ACK 71#2] 49736 > ftp [ACK] Seq=98 Ack=294 Win=65047 Len=0
Frame 76: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 98, Ack: 294, Len: 0
No. Time Protocol Length Info
77 89.041426 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 77: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 405, Ack: 98, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
78 89.042081 TCP 62 [TCP Dup ACK 71#3] 49736 > ftp [ACK] Seq=98 Ack=294 Win=65047 Len=0
Frame 78: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 98, Ack: 294, Len: 0
No. Time Protocol Length Info
79 90.901416 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 79: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 405, Ack: 98, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
80 90.901988 TCP 62 [TCP Dup ACK 71#4] 49736 > ftp [ACK] Seq=98 Ack=294 Win=65047 Len=0
Frame 80: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 98, Ack: 294, Len: 0
No. Time Protocol Length Info
81 94.000587 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 81: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 405, Ack: 98, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
82 94.001269 TCP 62 [TCP Dup ACK 71#5] 49736 > ftp [ACK] Seq=98 Ack=294 Win=65047 Len=0
Frame 82: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 98, Ack: 294, Len: 0
No. Time Protocol Length Info
83 99.580475 FTP 92 [TCP Retransmission] Response: 200 Switching to ASCII mode.
Frame 83: 92 bytes on wire (736 bits), 92 bytes captured (736 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 405, Ack: 98, Len: 30
File Transfer Protocol (FTP)
No. Time Protocol Length Info
84 99.581110 TCP 62 [TCP Dup ACK 71#6] 49736 > ftp [ACK] Seq=98 Ack=294 Win=65047 Len=0
Frame 84: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 98, Ack: 294, Len: 0
No. Time Protocol Length Info
85 117.494304 FTP 70 Request: TYPE A
Frame 85: 70 bytes on wire (560 bits), 70 bytes captured (560 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: 49736 (49736), Dst Port: ftp (21), Seq: 98, Ack: 294, Len: 8
File Transfer Protocol (FTP)
No. Time Protocol Length Info
86 117.531119 TCP 62 ftp > 49736 [RST] Seq=294 Win=0 Len=0
Frame 86: 62 bytes on wire (496 bits), 62 bytes captured (496 bits)
Ethernet II
PPP-over-Ethernet Session
Point-to-Point Protocol
Internet Protocol Version 4
Transmission Control Protocol, Src Port: ftp (21), Dst Port: 49736 (49736), Seq: 294, Len: 0
editar
Eu verifiquei com outro servidor FTP que está sob meu controle e coisas estranhas agora (leia: não está funcionando com isso também). De acordo com o meu servidor, ele está se comunicando com um endereço IPv4 que termina em .0 . Para o registro, estou localizado na Alemanha. Eu nunca vi um endereço IPv4 terminando em .0 antes.
Se eu verificar o roteador no lado do cliente, ele reportará um endereço IPv4 público completamente diferente (pelo menos aquele parece válido) e também reportará um endereço IPv6 (extremamente raramente na Alemanha para ter um. Depende do ISP.)
E os logs do meu servidor estão dizendo que ele está enviando (e também retransmitindo, como não está recebendo uma ACK ) a mensagem Entering passive mode . O que significa, pelo menos para mim, que o ISP está perdendo / perdendo esse pacote.
Devo entrar em contato com o ISP com essa informação?
Isso provavelmente será causado por um problema de firewall. em sua configuração do proftpd, limite as portas que ele usará
PassivePorts 61000 61199
Isso limitará as portas passivas de 61000 para 61199. Agora, verifique se essas portas estão abertas no seu firewall.
Há um ótimo artigo sobre isso aqui