问题遇到的现象和发生背景
[mszhaowei@login10 ~]$ git clone https://github.com/llvm/llvm-project.git
Cloning into 'llvm-project'
fatal: unable to access 'https://github.com/llvm/llvm-project.git/': Failed connect to github.com:443; Connection timed out
[mszhaowei@login10 ~]$ git clone https://github.com/llvm/llvm-project.git
Cloning into 'llvm-project'
fatal: unable to access 'https://github.com/llvm/llvm-project.git/': Failed connect to github.com:443; Connection timed out