下面的调试信息或者会有帮助。
$ git fetch
Bad packet length 1397966893.
Disconnecting: Packet corrupt
fatal: The remote end hung up unexpectedly
$ ssh -T git@coding.net -vvv
OpenSSH_5.9p1 Debian-5ubuntu1.4, OpenSSL 1.0.1 14 Mar 2012
debug1: Reading configuration data /home/honwhy/.ssh/config
debug1: /home/honwhy/.ssh/config line 1: Applying options for coding.net
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to coding.net [118.192.93.38] port 22.
debug1: Connection established.
debug3: Incorrect RSA1 identifier
debug3: Could not load "/home/honwhy/.ssh/coding_rsa" as a RSA1 public key
debug1: identity file /home/honwhy/.ssh/coding_rsa type 1
debug1: Checking blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking blacklist file /etc/ssh/blacklist.RSA-2048
debug1: identity file /home/honwhy/.ssh/coding_rsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.2
debug1: match: OpenSSH_6.2 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.9p1 Debian-5ubuntu1.4
debug2: fd 3 setting O_NONBLOCK
debug3: load_hostkeys: loading entries for host "coding.net" from file "/home/honwhy/.ssh/known_hosts"
debug3: load_hostkeys: loaded 0 keys
debug1: SSH2_MSG_KEXINIT sent
Bad packet length 1397966893.
Disconnecting: Packet corrupt
经过我的搜索，问题解决了
参考这两个链接
https://blog.flameeyes.eu/2011/01/mostly-unknown-openssh-tricks
https://blogs.oracle.com/janp/entry/ssh_messages_code_bad_packet
以下是修改后的
~/.ssh/config配置这两行配置比较重要
第一次链接时还是会提示错误，第二次链接就可以正常连接了。
详细过程真的应该去读读手册、或者RFC，第二个链接中也说得很具体了。