[9fans] sshnet and the go dns resolver

[9fans] sshnet and the go dns resolver

[Steve Simon]

hi,

the senerio - i have a plan9 terminal, a mac laptop. the laptop connects to a vpn.

i write in go, and thus far i use sshfs to mount the mac’s filesystem and edit my code. i build and run the code on the mac.

i thought i could use git9 via sshnet to work natively on plan9

most of this is fine but when go tries to access mod files for packages on the vpn i get a “no sutiable address found” error for proxy.golang.org.

i can resce the address i need (over the vpn) using ndb/dnsquery however.

if i try and build without my sshnet vpn connection then i get a different error which refers to a repository on the vpn.

so. i think the native resolver in the go libraries (and thus in the go executable) do not play nicely with sshnet.

my guess (only a guess) is go is trying to do its own name resolution using udp port 53 and sshnet does not support udp.

anyone any ideas?
can i convince go to use plan9’s own name resolution?
can ssh (and thus sshnet) forward udp or is that not possible?

thanks for any ideas

-Steve



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Re: [9fans] sshnet and the go dns resolver

[Fazlul Shahriar]

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The Go net package uses /net/cs and /net/dns. I see sshnet doesn't create
/net/dns. That could be the issue.

fhs

On Tue, Feb 23, 2021 at 4:35 PM Steve Simon <steve@quintile.net> wrote:

> hi,
> 
> the senerio - i have a plan9 terminal, a mac laptop. the laptop connects
> to a vpn.
> 
> i write in go, and thus far i use sshfs to mount the mac’s filesystem and
> edit my code. i build and run the code on the mac.
> 
> i thought i could use git9 via sshnet to work natively on plan9
> 
> most of this is fine but when go tries to access mod files for packages on
> the vpn i get a “no sutiable address found” error for proxy.golang.org.
> 
> i can resce the address i need (over the vpn) using ndb/dnsquery however.
> 
> if i try and build without my sshnet vpn connection then i get a different
> error which refers to a repository on the vpn.
> 
> so. i think the native resolver in the go libraries (and thus in the go
> executable) do not play nicely with sshnet.
> 
> my guess (only a guess) is go is trying to do its own name resolution
> using udp port 53 and sshnet does not support udp.
> 
> anyone any ideas?
> can i convince go to use plan9’s own name resolution?
> can ssh (and thus sshnet) forward udp or is that not possible?
> 
> thanks for any ideas
> 
> -Steve
> 

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Re: [9fans] sshnet and the go dns resolver

[Jeff Sickel]

I’ve noticed similar problems with go programs and resolving a lookup.
There are go programs that explicitly look for “/etc/resolv.conf” to
grab the nameserver to use, though it would be nice if the developer
were using the default net package for lookups.


> On Feb 23, 2021, at 3:34 PM, Steve Simon <steve@quintile.net> wrote:
> 
> hi,
> 
> the senerio - i have a plan9 terminal, a mac laptop. the laptop connects to a vpn.
> 
> i write in go, and thus far i use sshfs to mount the mac’s filesystem and edit my code. i build and run the code on the mac.
> 
> i thought i could use git9 via sshnet to work natively on plan9
> 
> most of this is fine but when go tries to access mod files for packages on the vpn i get a “no sutiable address found” error for proxy.golang.org.
> 
> i can resce the address i need (over the vpn) using ndb/dnsquery however.
> 
> if i try and build without my sshnet vpn connection then i get a different error which refers to a repository on the vpn.
> 
> so. i think the native resolver in the go libraries (and thus in the go executable) do not play nicely with sshnet.
> 
> my guess (only a guess) is go is trying to do its own name resolution using udp port 53 and sshnet does not support udp.
> 
> anyone any ideas?
> can i convince go to use plan9’s own name resolution?
> can ssh (and thus sshnet) forward udp or is that not possible?
> 
> thanks for any ideas
> 
> -Steve
> 

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Re: [9fans] sshnet and the go dns resolver

[Steve Simon]

thanks all for the suggestions.

digging through the source of sshnet.c and the go net library i think i understand.

the plan9 runtime library assumes, and insists the string returned from /net/cs contains a valid ip address.

the code in sshnet which serves a  /net/cs does a local ndb lookup, and if that fails, returns the dns name it was given. i guess this is to allow name resolution to be tried at the remote host.

i shall experiment a bit more.

-Steve



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