由于某些未知原因，如果我从 NAT 网络内部连接到端口转发的 SSH 服务器，我的 SSH 客户端将挂起。如果我通过 NAT 路由器从网络外部（例如，从 EC2 实例）进行 SSH，则它可以正常工作。如果我从 NAT 网络内的一台主机通过 SSH 连接到另一台主机，它也可以正常工作。如果我通过 SSH 连接到 NAT 路由器的公共或私有地址上的转发端口 22，则 SSH 客户端将挂起。
Host A (private: A.A.A.A): SSH Client
HOST B (private: B.B.B.B): SSH Server
EC2 Host (public: E.E.E.E): SSH Client
ROUTER (Public: R.R.R.R): NAT Router
ROUTER (private: r.r.r.r): NAT Router
这是我凭经验发现的
A.A.A.A -> B.B.B.B works
B.B.B.B -> A.A.A.A works
E.E.E.E -> R.R.R.R -> B.B.B.B works
A.A.A.A -> R.R.R.R -> B.B.B.B does not work
A.A.A.A -> r.r.r.r -> B.B.B.B does not work
SSH 客户端在挂起之前发出的最后一条消息是
debug1: client_input_global_request: rtype [email protected] want_reply 0
这是从主机 A 连接到路由器的私有地址时的 ssh 日志：
OpenSSH_7.4p1, OpenSSL 1.0.2k 26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "10.0.0.1" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 10.0.0.1 [10.0.0.1] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 10.0.0.1:22 as 'me'
debug3: put_host_port: [10.0.0.1]:22
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:8
debug3: load_hostkeys: loaded 1 keys from [10.0.0.1]:22
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:2C4WXSvT20pE6QlmenhYFyO1TdTAth9MsbN86nYGi7s
debug3: put_host_port: [10.0.0.1]:22
debug3: put_host_port: [10.0.0.1]:22
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:8
debug3: load_hostkeys: loaded 1 keys from [10.0.0.1]:22
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:8
debug3: load_hostkeys: loaded 1 keys from [10.0.0.1]:22
debug1: Host '[10.0.0.1]:22' is known and matches the ECDSA host key.
debug1: Found key in /home/me/.ssh/known_hosts:8
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug2: key: /home/me/.ssh/id_rsa ((nil))
debug2: key: /home/me/.ssh/id_dsa ((nil))
debug2: key: /home/me/.ssh/id_ecdsa ((nil))
debug2: key: /home/me/.ssh/id_ed25519 ((nil))
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
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: /home/me/.ssh/id_rsa
debug3: no such identity: /home/me/.ssh/id_rsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_dsa
debug3: no such identity: /home/me/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_ecdsa
debug3: no such identity: /home/me/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_ed25519
debug3: no such identity: /home/me/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 52
debug1: Authentication succeeded (password).
Authenticated to 10.0.0.1 ([10.0.0.1]:22).
debug2: fd 5 setting O_NONBLOCK
debug3: fd 6 is O_NONBLOCK
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network
debug3: receive packet: type 80
debug1: client_input_global_request: rtype [email protected] want_reply 0
这是从 A 直接连接到 B 时的 ssh 日志：
OpenSSH_7.4p1, OpenSSL 1.0.2k 26 Jan 2017
debug1: Reading configuration data /etc/ssh/ssh_config
debug2: resolving "10.0.0.2" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 10.0.0.2 [10.0.0.2] port 22.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_rsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_rsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_dsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_dsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ecdsa type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ecdsa-cert type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ed25519 type -1
debug1: key_load_public: No such file or directory
debug1: identity file /home/me/.ssh/id_ed25519-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.4
debug1: match: OpenSSH_7.4 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to 10.0.0.2:22 as 'me'
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from 10.0.0.2
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: curve25519-sha256,[email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:2C4WXSvT20pE6QlmenhYFyO1TdTAth9MsbN86nYGi7s
debug3: hostkeys_foreach: reading file "/home/me/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /home/me/.ssh/known_hosts:1
debug3: load_hostkeys: loaded 1 keys from 10.0.0.2
debug1: Host '10.0.0.2' is known and matches the ECDSA host key.
debug1: Found key in /home/me/.ssh/known_hosts:1
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug2: key: /home/me/.ssh/id_rsa ((nil))
debug2: key: /home/me/.ssh/id_dsa ((nil))
debug2: key: /home/me/.ssh/id_ecdsa ((nil))
debug2: key: /home/me/.ssh/id_ed25519 ((nil))
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,ssh-rsa,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey,password
debug3: start over, passed a different list publickey,password
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: /home/me/.ssh/id_rsa
debug3: no such identity: /home/me/.ssh/id_rsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_dsa
debug3: no such identity: /home/me/.ssh/id_dsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_ecdsa
debug3: no such identity: /home/me/.ssh/id_ecdsa: No such file or directory
debug1: Trying private key: /home/me/.ssh/id_ed25519
debug3: no such identity: /home/me/.ssh/id_ed25519: No such file or directory
debug2: we did not send a packet, disable method
debug3: authmethod_lookup password
debug3: remaining preferred: ,password
debug3: authmethod_is_enabled password
debug1: Next authentication method: password
debug3: send packet: type 50
debug2: we sent a password packet, wait for reply
debug3: receive packet: type 52
debug1: Authentication succeeded (password).
Authenticated to 10.0.0.2 ([10.0.0.2]:22).
debug2: fd 5 setting O_NONBLOCK
debug3: fd 6 is O_NONBLOCK
debug1: channel 0: new [client-session]
debug3: ssh_session2_open: channel_new: 0
debug2: channel 0: send open
debug3: send packet: type 90
debug1: Requesting [email protected]
debug3: send packet: type 80
debug1: Entering interactive session.
debug1: pledge: network
debug3: receive packet: type 80
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug3: receive packet: type 91
debug2: callback start
debug2: fd 3 setting TCP_NODELAY
debug3: ssh_packet_set_tos: set IP_TOS 0x08
debug2: client_session2_setup: id 0
debug1: Sending command: ls
debug2: channel 0: request exec confirm 1
debug3: send packet: type 98
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel 0: rcvd adjust 2097152
debug3: receive packet: type 99
debug2: channel_input_status_confirm: type 99 id 0
debug2: exec request accepted on channel 0
aur
bin
documents
keys
lib
music
photos
src
debug3: receive packet: type 96
debug2: channel 0: rcvd eof
debug2: channel 0: output open -> drain
debug2: channel 0: obuf empty
debug2: channel 0: close_write
debug2: channel 0: output drain -> closed
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug3: receive packet: type 98
debug1: client_input_channel_req: channel 0 rtype [email protected] reply 0
debug2: channel 0: rcvd eow
debug2: channel 0: close_read
debug2: channel 0: input open -> closed
debug3: receive packet: type 97
debug2: channel 0: rcvd close
debug3: channel 0: will not send data after close
debug2: channel 0: almost dead
debug2: channel 0: gc: notify user
debug2: channel 0: gc: user detached
debug2: channel 0: send close
debug3: send packet: type 97
debug2: channel 0: is dead
debug2: channel 0: garbage collecting
debug1: channel 0: free: client-session, nchannels 1
debug3: channel 0: status: The following connections are open:
#0 client-session (t4 r0 i3/0 o3/0 fd -1/-1 cc -1)
debug3: send packet: type 1
debug1: fd 1 clearing O_NONBLOCK
debug3: fd 2 is not O_NONBLOCK
Transferred: sent 1816, received 2780 bytes, in 0.1 seconds
Bytes per second: sent 17844.2, received 27316.5
debug1: Exit status 0
答案1
这实际上是 NAT 的正常行为。为了解决这个问题，一种常见的做法是使用本地 DNS 强制解析到私有 IP 地址，而不是公共 IP 地址。
例如，主机 B 将具有 RRRR 的公共 DNS 记录，以便世界其他地方可以访问它。但是，如果您更改本地 DNS（或主机 A 上的 /etc/hosts 文件）以强制主机 B 的主机名解析为 BBBB，则您可以在本地对服务器进行寻址。
显然，此方法仅在使用 DNS 时才有效，但由于这种 NAT 行为，我非常依赖此方法。此外，如果您连接到本地资源，尤其是在较大的网络上，请求到达路由器并没有多大意义。
本文介绍了这种类型的 NAT 行为，以及如果您不想使用 DNS 时使用 iptables 的可能解决方案：http://www.the-art-of-web.com/system/iptables-nat/