Bugzilla

We currently only disable prefetch to avoid doing dns if the porxy was manually configured, not when it was configured through system proxy/PAC scripts.

[netwerk/dns/DNSServiceBase.cpp#52-60](https://searchfox.org/mozilla-central/rev/c09764753ea40725eb50decad2c51edecbd33308/netwerk/dns/DNSServiceBase.cpp#52-60)
```cpp
// We should avoid doing DNS when a proxy is in use.
if (StaticPrefs::network_proxy_type() ==
        nsIProtocolProxyService::PROXYCONFIG_MANUAL &&
    mHasSocksProxy && StaticPrefs::network_proxy_socks_remote_dns()) {
  // Allow IP lookups through, but nothing else.
  if (!HostIsIPLiteral(aHostname)) {
    return true;
  }
}
```

This should probably don't use the StaticPrefs to determine whether socks_remote_dns is enabled, but look into the ProxyInfo and determine whether the `TRANSPARENT_PROXY_RESOLVES_HOST` flag is set.

[netwerk/base/nsIProxyInfo.idl#100-105](https://searchfox.org/mozilla-central/rev/c09764753ea40725eb50decad2c51edecbd33308/netwerk/base/nsIProxyInfo.idl#100-105)
```cpp
/**
 * This flag is set if the proxy is to perform name resolution itself.  If
 * this is the case, the hostname is used in some fashion, and we shouldn't
 * do any form of DNS lookup ourselves.
 */
const unsigned short TRANSPARENT_PROXY_RESOLVES_HOST = 1 << 0;
```

We currently only disable prefetch to avoid doing dns if the proxy was manually configured, not when it was configured through system proxy/PAC scripts.

[netwerk/dns/DNSServiceBase.cpp#52-60](https://searchfox.org/mozilla-central/rev/c09764753ea40725eb50decad2c51edecbd33308/netwerk/dns/DNSServiceBase.cpp#52-60)
```cpp
// We should avoid doing DNS when a proxy is in use.
if (StaticPrefs::network_proxy_type() ==
        nsIProtocolProxyService::PROXYCONFIG_MANUAL &&
    mHasSocksProxy && StaticPrefs::network_proxy_socks_remote_dns()) {
  // Allow IP lookups through, but nothing else.
  if (!HostIsIPLiteral(aHostname)) {
    return true;
  }
}
```

This should probably don't use the StaticPrefs to determine whether socks_remote_dns is enabled, but look into the ProxyInfo and determine whether the `TRANSPARENT_PROXY_RESOLVES_HOST` flag is set.

[netwerk/base/nsIProxyInfo.idl#100-105](https://searchfox.org/mozilla-central/rev/c09764753ea40725eb50decad2c51edecbd33308/netwerk/base/nsIProxyInfo.idl#100-105)
```cpp
/**
 * This flag is set if the proxy is to perform name resolution itself.  If
 * this is the case, the hostname is used in some fashion, and we shouldn't
 * do any form of DNS lookup ourselves.
 */
const unsigned short TRANSPARENT_PROXY_RESOLVES_HOST = 1 << 0;
```