大学网络下Windows机器SSH克隆GitHub私有仓库失败求助

在大学网络环境的Windows机器上，使用SSH克隆GitHub私有仓库时，进程会卡住数分钟后失败，判断是连接断开导致。已确认IP地址完全可路由，防火墙未拦截任何流量，HTTPS克隆正常，但SSH克隆失败。

调试日志 #

C:\Users\[User]\Documents\test>set GIT_SSH_COMMAND=ssh -v

C:\Users\[User]\Documents\test>git clone git@github.com:SvenDNA/homepage.git
Cloning into 'homepage'...
OpenSSH_9.9p1, OpenSSL 3.2.3 3 Sep 2024
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to github.com [140.82.121.3] port 22.
debug1: Connection established.
debug1: identity file /c/Users/[User]/.ssh/id_rsa type 0
debug1: identity file /c/Users/[User]/.ssh/id_rsa-cert type -1
debug1: identity file /c/Users/[User]/.ssh/id_ecdsa type -1
debug1: identity file /c/Users/[User]/.ssh/id_ecdsa-cert type -1
debug1: identity file /c/Users/[User]/.ssh/id_ecdsa_sk type -1
debug1: identity file /c/Users/[User]/.ssh/id_ecdsa_sk-cert type -1
debug1: identity file /c/Users/[User]/.ssh/id_ed25519 type -1
debug1: identity file /c/Users/[User]/.ssh/id_ed25519-cert type -1
debug1: identity file /c/Users/[User]/.ssh/id_ed25519_sk type -1
debug1: identity file /c/Users/[User]/.ssh/id_ed25519_sk-cert type -1
debug1: identity file /c/Users/[User]/.ssh/id_xmss type -1
debug1: identity file /c/Users/[User]/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_9.9
debug1: Remote protocol version 2.0, remote software version babeld-cd94d92b7
debug1: compat_banner: no match: babeld-cd94d92b7
debug1: Authenticating to github.com:22 as 'git'
debug1: load_hostkeys: fopen /c/Users/[User]/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: curve25519-sha256
debug1: kex: host key algorithm: ssh-ed25519
debug1: kex: server->client cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: kex: client->server cipher: chacha20-poly1305@openssh.com MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: SSH2_MSG_KEX_ECDH_REPLY received
debug1: Server host key: ssh-ed25519 SHA256:+DiY3wvvV6TuJJhbpZisF/zLDA0zPMSvHdkr4UvCOqU
debug1: load_hostkeys: fopen /c/Users/[User]/.ssh/known_hosts2: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts: No such file or directory
debug1: load_hostkeys: fopen /etc/ssh/ssh_known_hosts2: No such file or directory
debug1: Host 'github.com' is known and matches the ED25519 host key.
debug1: Found key in /c/Users/[User]/.ssh/known_hosts:1
debug1: ssh_packet_send2_wrapped: resetting send seqnr 3
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: ssh_packet_read_poll2: resetting read seqnr 3
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_ext_info_client_parse: server-sig-algs=<ssh-ed25519-cert-v01@openssh.com,ecdsa-sha2-nistp521-cert-v01@openssh.com,ecdsa-sha2-nistp384-cert-v01@openssh.com,ecdsa-sha2-nistp256-cert-v01@openssh.com,sk-ssh-ed25519-cert-v01@openssh.com,sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,rsa-sha2-512-cert-v01@openssh.com,rsa-sha2-256-cert-v01@openssh.com,ssh-rsa-cert-v01@openssh.com,sk-ssh-ed25519@openssh.com,sk-ecdsa-sha2-nistp256@openssh.com,ssh-ed25519,ecdsa-sha2-nistp521,ecdsa-sha2-nistp384,ecdsa-sha2-nistp256,rsa-sha2-512,rsa-sha2-256,ssh-rsa>
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Will attempt key: /c/Users/[User]/.ssh/id_rsa RSA SHA256:zYCuDer+slWMsl+qHWyrRVWzZqcTSXjdf1KBobFsWGY
debug1: Will attempt key: /c/Users/[User]/.ssh/id_ecdsa
debug1: Will attempt key: /c/Users/[User]/.ssh/id_ecdsa_sk
debug1: Will attempt key: /c/Users/[User]/.ssh/id_ed25519
debug1: Will attempt key: /c/Users/[User]/.ssh/id_ed25519_sk
debug1: Will attempt key: /c/Users/[User]/.ssh/id_xmss
debug1: Offering public key: /c/Users/[User]/.ssh/id_rsa RSA SHA256:zYCuDer+slWMsl+qHWyrRVWzZqcTSXjdf1KBobFsWGY
debug1: Server accepts key: /c/Users/[User]/.ssh/id_rsa RSA SHA256:zYCuDer+slWMsl+qHWyrRVWzZqcTSXjdf1KBobFsWGY
Authenticated to github.com ([140.82.121.3]:22) using "publickey".
debug1: channel 0: new session [client-session] (inactive timeout: 0)
debug1: Entering interactive session.
debug1: pledge: filesystem
debug1: client_input_global_request: rtype hostkeys-00@openssh.com want_reply 0
debug1: client_input_hostkeys: searching /c/Users/[User]/.ssh/known_hosts for github.com / (none)
debug1: client_input_hostkeys: searching /c/Users/[User]/.ssh/known_hosts2 for github.com / (none)
debug1: client_input_hostkeys: hostkeys file /c/Users/[User]/.ssh/known_hosts2 does not exist
debug1: client_input_hostkeys: no new or deprecated keys from server
debug1: Sending environment.
debug1: channel 0: setting env GIT_PROTOCOL = "version=2"
debug1: Sending command: git-upload-pack 'SvenDNA/homepage.git'
debug1: pledge: fork
remote: Enumerating objects: 910, done.
remote: Counting objects: 100% (910/910), done.
remote: Compressing objects: 100% (702/702), done.
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
debug1: client_input_global_request: rtype keepalive@openssh.com want_reply 1
Connection to github.com closed by remote host.
client_loop: send disconnect: Broken pipe
fetch-pack: unexpected disconnect while reading sideband packet
fatal: early EOF
fatal: fetch-pack: invalid index-pack output

从日志来看，SSH认证已成功，但在传输压缩后的仓库对象时连接被远程主机断开，大概率是大学网络对SSH端口（22）的流量做了限流或QoS策略，也可能是长连接无数据交互被网关主动切断。以下是可行的解决办法：

• 改用GitHub的SSH 443端口连接
  GitHub支持在443端口提供SSH服务，多数网络对443端口的限制远低于22端口。操作步骤：

  1. 在Windows用户目录的.ssh文件夹下，创建或编辑名为config的无后缀文件
  2. 添加以下配置内容：

     Host github.com
         Hostname ssh.github.com
         Port 443
         User git
     

  保存后，直接使用原SSH克隆命令即可。

• 开启SSH连接心跳保活
  网络长时间无数据传输时，网关可能主动断开连接。开启心跳包可维持连接：
  在上述config文件中添加或补充：

  Host github.com
         ServerAliveInterval 30
         ServerAliveCountMax 5
  

  该配置会每30秒发送一次心跳包，连续5次未收到回应才断开连接。

• 降低Git压缩级别或禁用压缩
  高压缩的仓库数据传输可能触发网络限流，尝试调整Git压缩设置：

  git config --global core.compression 0
  

  或在克隆时临时禁用压缩：

  git clone git@github.com:SvenDNA/homepage.git --no-compression
  

• 使用浅克隆减少传输数据量
  如果不需要仓库完整历史，可只克隆最近的提交：

  git clone git@github.com:SvenDNA/homepage.git --depth 1
  

  后续若需要完整历史，执行git fetch --unshallow即可。

内容的提问来源于stack exchange，提问作者SvenDNA