Makes BrokerChannel abstract over a rendezvousMethod. BrokerChannel
itself is responsible for keepLocalAddresses and the NAT type state, as
well as encoding and decoding client poll messages. rendezvousMethod is
only responsible for delivery of encoded messages.
Formerly, BrokerChannel represented the broker URL and possible domain
fronting as
bc.url *url.URL
bc.Host string
That is, bc.url is the URL of the server which we contact directly, and
bc.Host is the Host header to use in the request. With no domain
fronting, bc.url points directly at the broker itself, and bc.Host is
blank. With domain fronting, we do the following reshuffling:
if front != "" {
bc.Host = bc.url.Host
bc.url.Host = front
}
That is, we alter bc.url to reflect that the server to which we send
requests directly is the CDN, not the broker, and store the broker's own
URL in the HTTP Host header.
The above representation was always confusing to me, because in my
mental model, we are always conceptually communicating with the broker;
but we may optionally be using a CDN proxy in the middle. The new
representation is
bc.url *url.URL
bc.front string
bc.url is the URL of the broker itself, and never changes. bc.front is
the optional CDN front domain, and likewise never changes after
initialization. When domain fronting is in use, we do the swap in the
http.Request struct, not in BrokerChannel itself:
if bc.front != "" {
request.Host = request.URL.Host
request.URL.Host = bc.front
}
Compare to the representation in meek-client:
https://gitweb.torproject.org/pluggable-transports/meek.git/tree/meek-client/meek-client.go?h=v0.35.0#n94
var options struct {
URL string
Front string
}
https://gitweb.torproject.org/pluggable-transports/meek.git/tree/meek-client/meek-client.go?h=v0.35.0#n308
if ok { // if front is set
info.Host = info.URL.Host
info.URL.Host = front
}
The tests were using a broker URL of "test.broker" (i.e., a schema-less,
host-less, relative path), and running assertions on the value of
b.url.Path. This is strange, especially in tests regarding domain
fronting, where we care about b.url.Host, not b.url.Path. This commit
changes the broker URL to "http://test.broker" and changes tests to
check b.url.Host. I also added an additional assertion for an empty
b.Host in the non-domain-fronted case.
The race condition occurs because concurrent goroutines are intermixing
reads and writes of `WebRTCPeer.closed`.
Spotted when integrating Snowflake inside OONI in
https://github.com/ooni/probe-cli/pull/373.
Send the client poll request and response in a json-encoded format in
the HTTP request body rather than sending the data in HTTP headers. This
will pave the way for using domain-fronting alternatives for the
Snowflake rendezvous.
Bug #21314: maintains a separate snowflake connect loop per SOCKS
connection. This way, if Tor decides to stop using Snowflake, Snowflake
will stop using the client's network.
Do it as a side effect of NewWebRTCPeer.
Remove WebRTCPeer tests as they currently require invasively modifying
internal fields at different stages of construction.
The other interfaces in client/lib/interfaces.go exist for the purpose
of running tests, but not Snowflake. Existing code would not have worked
with other types anyway, because it does unchecked .(*WebRTCPeer)
conversions.
We are no longer checking for nil BrokerChannels in Catch because this
case is caught from the return values of NewBrokerChannel. This change
caused a no longer necessary unit test to hang.
There were a few tests that needed refreshing since the introduction of
the pion library. Also added a few tests for the ICE server parsing
function in the client.
Modified the snowflake client to use pion/webrtc as the webrtc library.
This involved a few small changes to match function signatures as well
as several larger ones:
- OnNegotiationNeeded is no longer supported, so CreateOffer and
SetLocalDescription have been moved to a go routine called after the
other peer connection callbacks are set
- We need our own deserialize/serialize functions
- We need to use a SettingEngine in order to access the
OnICEGatheringStateChange callback
