SSH 连接慢: Get POSSIBLE BREAK-IN ATTEMPT msg when i ssh to s server

核心：

服务器端sshd配置文件 /etc/ssh/sshd_config 看是否有如下的两条配置条目

GSSAPIAuthentication no
UseDNS no

如果前面带#，请把#删掉，或者新添加入这样两行。
然后重启sshd服务，或者重启服务器也可以。

注意是文件 /etc/ssh/sshd_config 而不是/etc/ssh/ssh_config

ssh 登录远程服务器，速度非常慢，通过网上查询，发现有一个参数 -v 可以输出显示连接的具体消息。于是连接加上这个参数连接

[feng@fsc ~]$ ssh -v foo.path8.net
OpenSSH_5.3p1, OpenSSL 1.0.0-fips 29 Mar 2010
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to v.path8.net [64.120.xxx.xxx] port 22.
debug1: Connection established.
debug1: identity file /home/feng/.ssh/identity type -1
debug1: identity file /home/feng/.ssh/id_rsa type 1
debug1: identity file /home/feng/.ssh/id_dsa type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
debug1: match: OpenSSH_5.3 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
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
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host 'v.path8.net' is known and matches the RSA host key.
debug1: Found key in /home/feng/.ssh/known_hosts:4
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug1: Next authentication method: gssapi-with-mic
/*--------- 这里停留的十多秒钟时间 ----------*/
reverse mapping checking getaddrinfo for srv3.mktmaster.net [64.120.xxx.xxx] failed - POSSIBLE BREAK-IN ATTEMPT!
debug1: Unspecified GSS failure.  Minor code may provide more information
Credentials cache file '/tmp/krb5cc_501' not found

debug1: Unspecified GSS failure.  Minor code may provide more information
Credentials cache file '/tmp/krb5cc_501' not found

debug1: Unspecified GSS failure.  Minor code may provide more information

debug1: Next authentication method: publickey
debug1: Offering public key: /home/feng/.ssh/id_rsa
debug1: Server accepts key: pkalg ssh-rsa blen 277
debug1: Authentication succeeded (publickey).
debug1: channel 0: new [client-session]
debug1: Requesting [e-mail]
debug1: Entering interactive session.
debug1: Sending environment.
debug1: Sending env XMODIFIERS = @im=ibus
debug1: Sending env LANG = zh_CN.utf8
Last login: Mon Oct 24 10:26:30 2011 from 124.79.xxx.xxx
[feng@v ~]$

大概就是GSSAPIAuthentication这个参数的问题了，之前就是因为连接速度慢，网上查，说是/etc/ssh/sshd_config 里加入参数 UseDNS no，再加个GSSAPIAuthentication yes, 结果速度还是慢。
于是去把这行改为GSSAPIAuthentication no，重启服务器端的ssdh服务，再次连接，速度快多了。