Conexão SSH lenta para estabelecer: possíveis razões?

Question

Eu recentemente atualizei meu desktop para o Windows 7 e o abri para o ssh de outras caixas (usando o OpenSSH como instalado com o Cygwin).

Tudo funciona - no entanto, há um atraso muito longo (às vezes até 30 segundos) quando tento fazer a conexão pela primeira vez (antes de solicitar a senha), mesmo a partir de uma conexão com fio. Não há tal atraso quando eu ssh remotamente para minhas caixas no trabalho.

Ficarei muito grato por suas ideias sobre o que posso fazer para depurar isso. Eu reconheço que há um zilhão de pequenas coisas que afetam a velocidade de estabelecer uma conexão ssh, mas isso parece tão drasticamente ruim que deve haver algo de errado.

ssh -vvv output segue (warning: long) - uma longa pausa é após listar os arquivos de identidade ( identity file /Users/Arkaaito/... ), e depois há outra longa pausa depois de listar as chaves ( key: /Users/Arkaaito... ). Suponho que seja apenas porque ainda não tenho a autenticação baseada em chave configurada. (Ironicamente, eu queria esperar para adicionar isso até que eu trabalhasse com autenticação baseada em senha, na rede interna.)

Arkas-MacBook-Pro:~ Arkaaito$ ssh -vvv [email protected]
OpenSSH_5.2p1, OpenSSL 0.9.8l 5 Nov 2009
debug1: Reading configuration data /etc/ssh_config
debug2: ssh_connect: needpriv 0
debug1: Connecting to 192.168.0.196 [192.168.0.196] port 22.
debug1: Connection established.
debug1: identity file /Users/Arkaaito/.ssh/identity type -1
debug1: identity file /Users/Arkaaito/.ssh/id_rsa type -1
debug1: identity file /Users/Arkaaito/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.1
debug1: match: OpenSSH_5.1 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.2
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,[email protected]
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: none,[email protected],zlib
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: first_kex_follows 0 
debug2: kex_parse_kexinit: reserved 0 
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,[email protected],aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit: aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,arcfour128,arcfour256,arcfour,aes192-cbc,aes256-cbc,[email protected],aes128-ctr,aes192-ctr,aes256-ctr
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,[email protected],hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit: none,[email protected]
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: 
debug2: kex_parse_kexinit: first_kex_follows 0 
debug2: kex_parse_kexinit: reserved 0 
debug2: mac_setup: found hmac-md5
debug1: kex: server->client aes128-ctr hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug2: dh_gen_key: priv key bits set: 127/256
debug2: bits set: 521/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: check_host_in_hostfile: filename /Users/Arkaaito/.ssh/known_hosts
debug3: check_host_in_hostfile: match line 16
debug1: Host '192.168.0.196' is known and matches the RSA host key.
debug1: Found key in /Users/Arkaaito/.ssh/known_hosts:16
debug2: bits set: 522/1024
debug1: ssh_rsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /Users/Arkaaito/.ssh/identity (0x0)
debug2: key: /Users/Arkaaito/.ssh/id_rsa (0x0)
debug2: key: /Users/Arkaaito/.ssh/id_dsa (0x0)
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug3: start over, passed a different list publickey,password,keyboard-interactive
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Trying private key: /Users/Arkaaito/.ssh/identity
debug3: no such identity: /Users/Arkaaito/.ssh/identity
debug1: Trying private key: /Users/Arkaaito/.ssh/id_rsa
debug3: no such identity: /Users/Arkaaito/.ssh/id_rsa
debug1: Trying private key: /Users/Arkaaito/.ssh/id_dsa
debug3: no such identity: /Users/Arkaaito/.ssh/id_dsa
debug2: we did not send a packet, disable method
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred: password
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug2: we sent a keyboard-interactive packet, wait for reply
debug1: Authentications that can continue: publickey,password,keyboard-interactive
debug3: userauth_kbdint: disable: no info_req_seen
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: 
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
[email protected]'s password: 

    

Answer 1

Eu estaria disposto a apostar que é uma falta de DNS reverso. Tente desabilitar a pesquisa reversa de DNS no servidor e veja se isso ajuda.

    

Answer 2

Dê uma olhada no ssh_config e procure por GSSAPIAuthentication . Certifique-se de que o valor esteja definido como 'no'. No Ubuntu nos novos pacotes do openssh, isso vem ativado por padrão e eu experimentei atrasos de até 10 segundos conectando a hosts SSH até que eu desabilitei a opção.

    

Answer 3

Eu não sei se esse é o motivo, mas talvez seja o Autotuning? Você pode desativá-lo temporariamente para testar.

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