internal/delegatingresolver: avoid proxy if networktype of target address is not tcp

[eshitachandwani]

Fixes: #8207

RELEASE NOTES:

• Proxy connections are no longer attempted for targets with non-TCP network types.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.17%. Comparing base (5edab9e) to head (607ec91).
Report is 6 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8215      +/-   ##
==========================================
- Coverage   82.17%   82.17%   -0.01%     
==========================================
  Files         410      410              
  Lines       40236    40405     +169     
==========================================
+ Hits        33065    33203     +138     
- Misses       5822     5842      +20     
- Partials     1349     1360      +11     

Files with missing lines	Coverage Δ
.../resolver/delegatingresolver/delegatingresolver.go	83.67% <100.00%> (+1.45%)	⬆️

... and 35 files with indirect coverage changes

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[arjan-bal]

Here we're making an assumption that the network type of the first address of the endpoint is the same the address type of all remaining addresses. This may be true for most real-world usecases, but it isn't a requirement specified in the resolver API. It should not be too difficult to avoid proxying on a per-address basis. There are two places below where we do the following, one for resolver.State.Addresses and once for resolver.State.Endpoints:

proxyattributes.Set(proxyAddr, proxyattributes.Options{
	User:        r.proxyURL.User,
	ConnectAddr: targetAddr.Addr,
})

We can refactor this into a method that takes in the target address and proxy address and returns the combined address.

fn (r *delegatingResolver) combineAddresses(targetAddr, proxyAddr resolver.Address) resolver.Address {
    if  networktype.Get(targetAddr) != "tcp" {
        return targetAddr
    }
    return proxyattributes.Set(proxyAddr, proxyattributes.Options{
	User:        r.proxyURL.User,
	ConnectAddr: targetAddr.Addr,
    })
}

[arjan-bal]

The above comment end up adding duplicate addresses in the loop on targetResolverState.Endpoints. We will probably need to invert the loop on r.proxyAddrs and endpt.Addresses and break early:

for _, endpt := range (*r.targetResolverState).Endpoints {
	var addrs []resolver.Address
	for _, targetAddr := range endpt.Addresses {
                 if  networktype.Get(targetAddr) != "tcp" {
                          addrs = append(addrs, targetAddr)
                          continue
                  }
                  for _, proxyAddr := range r.proxyAddrs { 
			addrs = append(addrs, proxyattributes.Set(proxyAddr, proxyattributes.Options{
				User:        r.proxyURL.User,
				ConnectAddr: targetAddr.Addr,
			}))
		}
	}
	endpoints = append(endpoints, resolver.Endpoint{Addresses: addrs})
}

[eshitachandwani]

Right, done ! Also added a check in beginning , if there is not address with network type TCP , we do not wait for proxy update and just update the cc state.

[arjan-bal]

Please also fix the format of the release notes.

[arjan-bal]

Out here we're assuming !ok to be the same of tcp. However, the old code in the dialer used to parse the address string when !ok to determine the network type, we should probably maintain the same behaviour.

grpc-go/internal/transport/http2_client.go

Lines 177 to 182 in 172fc5b

	if !ok {
	networkType, address = parseDialTarget(address)
	}
	if networkType == "tcp" && useProxy {
	return proxyDial(ctx, address, grpcUA)
	}

[arjan-bal]

I think the code will be simpler if we refactor finding a TCP address in a helper function. The helper function can return early instead of keeping track of a isTCP boolean and breaking out of nested loops.

[arjan-bal]

nit: You can use continue in the if block to avoid indenting the else block.

[arjan-bal]

nit: You can use continue in the if block to avoid indenting the else block.