This commit replaces crypto/rand challenge generation with a blake2s-256
MAC. This enables the peer relay server to respond to multiple forward
disco.BindUDPRelayEndpoint messages per handshake generation without
sacrificing the proof of IP ownership properties of the handshake.
Responding to multiple forward disco.BindUDPRelayEndpoint messages per
handshake generation improves client address/path selection where
lowest client->server path/addr one-way delay does not necessarily
equate to lowest client<->server round trip delay.
It also improves situations where outbound traffic is filtered
independent of input, and the first reply
disco.BindUDPRelayEndpointChallenge message is dropped on the reply
path, but a later reply using a different source would make it through.
Reduction in serverEndpoint state saves 112 bytes per instance, trading
for slightly more expensive crypto ops: 277ns/op vs 321ns/op on an M1
Macbook Pro.
Updates tailscale/corp#34414
Signed-off-by: Jordan Whited <jordan@tailscale.com>
We can't relay a packet received over the IPv4 socket back out the same
socket if destined to an IPv6 address, and vice versa.
Updates tailscale/corp#30206
Signed-off-by: Jordan Whited <jordan@tailscale.com>
Relay handshakes may now occur multiple times over the lifetime of a
relay server endpoint. Handshake messages now include a handshake
generation, which is client specified, as a means to trigger safe
challenge reset server-side.
Relay servers continue to enforce challenge values as single use. They
will only send a given value once, in reply to the first arriving bind
message for a handshake generation.
VNI has been added to the handshake messages, and we expect the outer
Geneve header value to match the sealed value upon reception.
Remote peer disco pub key is now also included in handshake messages,
and it must match the receiver's expectation for the remote,
participating party.
Updates tailscale/corp#27502
Signed-off-by: Jordan Whited <jordan@tailscale.com>
The relay server now fetches IPs from local interfaces and external
perspective IP:port's via netcheck (STUN).
Updates tailscale/corp#27502
Signed-off-by: Jordan Whited <jordan@tailscale.com>
Commit 0841477 moved ServerEndpoint to an independent package. Move its
tests over as well.
Updates tailscale/corp#27502
Signed-off-by: Jordan Whited <jordan@tailscale.com>
ServerEndpoint will be used within magicsock and potentially elsewhere,
which should be possible without needing to import the server
implementation itself.
Updates tailscale/corp#27502
Signed-off-by: Jordan Whited <jordan@tailscale.com>
The previous strategy assumed clients maintained adequate state to
understand the relationship between endpoint allocation and the server
it was allocated on.
magicsock will not have awareness of the server's disco key
pre-allocation, it only understands peerAPI address at this point. The
second client to allocate on the same server could trigger
re-allocation, breaking a functional relay server endpoint.
If magicsock needs to force reallocation we can add opt-in behaviors
for this later.
Updates tailscale/corp#27502
Signed-off-by: Jordan Whited <jordan@tailscale.com>
tstime.GoDuration JSON serializes with time.Duration.String(), which is
more human-friendly than nanoseconds.
ServerEndpoint is currently experimental, therefore breaking changes
are tolerable.
Updates tailscale/corp#27502
Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit implements an experimental UDP relay server. The UDP relay
server leverages the Disco protocol for a 3-way handshake between
client and server, along with 3 new Disco message types for said
handshake. These new Disco message types are also considered
experimental, and are not yet tied to a capver.
The server expects, and imposes, a Geneve (Generic Network
Virtualization Encapsulation) header immediately following the underlay
UDP header. Geneve protocol field values have been defined for Disco
and WireGuard. The Geneve control bit must be set for the handshake
between client and server, and unset for messages relayed between
clients through the server.
Updates tailscale/corp#27101
Signed-off-by: Jordan Whited <jordan@tailscale.com>
