Why resolve the dns locally when using a socks5 proxy

Hi,

In the source code /lib/socks.c, there's the following line:

bool socks5_resolve_local =
    (conn->socks_proxy.proxytype == CURLPROXY_SOCKS5) ? TRUE : FALSE;
See
https://github.com/curl/curl/blob/12d655d4561cfee0103c57e791c59a263863e561/lib/socks.c#L385

It define's a boolean variable socks5_resolve_local, which is a flag to
decide whether to resolve dns locally. Apparently when the proxy is a
socks5 proxy, it would be true.

But the locally resolved IP address may not be accessible for the socks5
proxy server, which lead to an error message like:

curl: (7) Failed to receive SOCKS5 connect request ack.

Therefore, I wonder why does the variable exists. How about to remove it to
enable remote dns resolve since the socks5 protocol supports domain name as
its address type. See https://tools.ietf.org/html/rfc1928.

What's more, browsers like firefox provides an configuration entry
`network.proxy.socks_remote_dns` to enable socks5 remote resolving.

As far as I'm concerned, it's better for curl to have this feature.

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Received on 2019-08-15