HttpClient does not support IPv6 with scope ID on Mac or Linux

[mikeharder]

Repro Steps

1. Start an HTTP server on an IPv6 address with a scope ID. An example is the link-local address provided by running ifconfig.
2. Run curl to verify the server is working.
   2a. On Mac, I needed to wrap the IPv6 address with brackets, and escape the % as %25. For example: curl http://[fe80::blah%25en0]:1234/.
   2b. On Linux, I needed to not wrap with brackets, and not escape the %. For example: curl http://fe80::blah%eth0:1234/.
3. Call new HttpClient().GetAsync() using the same URL you passed to curl.

Expected
HttpClient works the same as curl itself.

Actual
HttpClient fails with an error like System.Net.Http.CurlException: Couldn't connect to server or System.UriFormatException: Invalid URI.

Notes
I tested many combinations of with/without brackets and with/without % encoded as %25, but none of them worked.

HttpClient on Windows does work correctly with IPv6 scope ID (tested with brackets and without encoding %).

Documentation for IPv6 scope ID support in Windows: https://msdn.microsoft.com/en-us/library/windows/desktop/aa385325(v=vs.85).aspx

Curl Versions
Mac

curl 7.37.1 (x86_64-apple-darwin14.0) libcurl/7.37.1 SecureTransport zlib/1.2.5
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtsp smtp smtps telnet tftp
Features: AsynchDNS GSS-Negotiate IPv6 Largefile NTLM NTLM_WB SSL libz

Linux

curl 7.35.0 (x86_64-pc-linux-gnu) libcurl/7.35.0 OpenSSL/1.0.1f zlib/1.2.8 libidn/1.28 librtmp/2.3
Protocols: dict file ftp ftps gopher http https imap imaps ldap ldaps pop3 pop3s rtmp rtsp smtp smtps telnet tftp
Features: AsynchDNS GSS-Negotiate IDN IPv6 Largefile NTLM NTLM_WB SSL libz TLS-SRP

[davidsh]

cc: @stephentoub

[stephentoub]

Thanks, Mike. I've investigated and know what and where the problem is, just determining what the right fix is.

[mikeharder]

Great. I'm happy to test the PR on my Mac and Linux machines, if you can tell me the easiest way to build the affected binaries and reference them from my project.

[stephentoub]

Thanks, @mikeharder. I put up a fix at dotnet/corefx#8249 which should hopefully address your problem (it fixes my local repro, e.g. I was able to use a url with HttpClient like http://[fe80::123:1234:1234:1234%eth0]:12345 successfully). If you can try it out locally, that'd be great... you can build just this component by cd'ing into corefx/src/System.Net.Http/src and doing msbuild /t:rebuild /p:OSGroup=Linux /v:m, and then overwriting your System.Net.Http.dll locally with the one produced... it'll need to be a relatively recent rc3 build to work, otherwise you'll likely get errors about some exports from System.Net.Http.Native.so/dylib not being found.

[mikeharder]

@stephentoub: How do I get a recent RC3 build? I am currently using the latest RC2 build from https://github.com/dotnet/cli.