Unable to connect to the ZeroTierOne service HTTP API via IPv4

[alexrsagen]

What you expect to be happening.

Should be able to connect to http://127.0.0.1:9993 (IPv4).

What is actually happening?

• Unable to connect to http://127.0.0.1:9993 (IPv4)
• Able to connect to http://[::1]:9993 (IPv6)
• Able to connect to http://localhost:9993, as it resolves to http://[::1]:9993 (IPv6)

Any steps to reproduce the error.

• Install ZeroTier One on Windows 11
• Start ZeroTier One service
• Start ZeroTier UI, observe message "Waiting for ZeroTier system service..." (source: https://github.com/zerotier/DesktopUI/blob/main/src/main.rs#L949)
• powershell -command "Test-NetConnection -ComputerName 127.0.0.1 -Port 9993"

Any relevant console output or screenshots.

C:\Windows\System32>whoami
nt-myndighet\system

C:\Windows\System32>netstat -a -o -n | findstr 9993 | findstr LISTENING
  TCP    0.0.0.0:9993           0.0.0.0:0              LISTENING       57760
  TCP    0.0.0.0:9993           0.0.0.0:0              LISTENING       57760
  TCP    [::]:9993              [::]:0                 LISTENING       57760

C:\Windows\System32>netstat -a -o -n | findstr 9993 | findstr UDP
  UDP    192.168.111.146:9993   *:*                                    57760
  UDP    192.168.111.155:9993   *:*                                    57760

C:\Windows\System32>tasklist | findstr 57760
zerotier-one_x64.exe         57760 Services                   0     13 520 K

C:\Windows\System32>powershell -command "Test-NetConnection -ComputerName 127.0.0.1 -Port 9993"
WARNING: TCP connect to (127.0.0.1 : 9993) failed

ComputerName           : 127.0.0.1
RemoteAddress          : 127.0.0.1
RemotePort             : 9993
InterfaceAlias         : Loopback Pseudo-Interface 1
SourceAddress          : 127.0.0.1
PingSucceeded          : True
PingReplyDetails (RTT) : 0 ms
TcpTestSucceeded       : False

C:\Windows\System32>powershell -command "Test-NetConnection -ComputerName '::1' -Port 9993"

ComputerName     : ::1
RemoteAddress    : ::1
RemotePort       : 9993
InterfaceAlias   : Loopback Pseudo-Interface 1
SourceAddress    : ::1
TcpTestSucceeded : True

C:\Windows\System32>powershell -command "test-netconnection -computername localhost -port 9993"

ComputerName     : localhost
RemoteAddress    : ::1
RemotePort       : 9993
InterfaceAlias   : Loopback Pseudo-Interface 1
SourceAddress    : ::1
TcpTestSucceeded : True

What operating system and ZeroTier version. Please try the latest ZeroTier release.

Windows 11 Business, build 10.0.22631.

ZeroTierOne version 1.14.0.

[laduke]

similar symptoms to #2151

[alexrsagen]

I may have identified the cause while reading through #2151... Correct me if I'm wrong, but this is my current assumption:

yhirose/cpp-httplib@b2203bb sets IPV6_V6ONLY to "no", making the IPv6 socket bind to both IPv4 and IPv6, leaving the IPv4 socket (or the IPv4 part of the IPv6 dual-stack socket?) unable to bind, as mentioned here.

ZeroTierOne explicitly binds to both IPv4 and IPv6, this is not valid while the IPV6_V6ONLY flag is set to "no".

To resolve the issue, ZeroTierOne should either:

• not utilize a dual-stack IPv6 socket (by explicitly setting IPV6_V6ONLY to "yes")
• only bind to a single dual-stack IPv6 socket (by removing the IPv4 bind)

[yhirose]

@alexrsagen I am an author of cpp-httplib, and I happened to find this issue. I made a change to allow users to adjust this socket behavior.

You can adjust the behavior with either CPPHTTPLIB_IPV6_V6ONLY processor macro, or set_ipv6_v6only method.
This change is included in v0.17.0. Hope it helps!