This change is for Linux only.
Previously, when running with multiple tun.routines, we would only have one file descriptor. This change instead sets IFF_MULTI_QUEUE and opens a file descriptor for each routine. This allows us to process with multiple threads while preventing out of order packet reception issues.
To attempt to distribute the flows across the queues, we try to write to the tun/UDP queue that corresponds with the one we read from. So if we read a packet from tun queue "2", we will write the outgoing encrypted packet to UDP queue "2". Because of the nature of how multi queue works with flows, a given host tunnel will be sticky to a given routine (so if you try to performance benchmark by only using one tunnel between two hosts, you are only going to be using a max of one thread for each direction).
Because this system works much better when we can correlate flows between the tun and udp routines, we are deprecating the undocumented "tun.routines" and "listen.routines" parameters and introducing a new "routines" parameter that sets the value for both. If you use the old undocumented parameters, the max of the values will be used and a warning logged.
Co-authored-by: Nate Brown <nbrown.us@gmail.com>
This commit updates the Interface.Inside type to be a new interface
type instead of a *Tun. This will allow for an inside interface
that does not use a tun device, such as a single-binary client that
can run without elevated privileges.
If different mtus are specified for different routes, we should set
advmss on each route because Linux does a poor job of selecting the
default (from ip-route(8)):
advmss NUMBER (Linux 2.3.15+ only)
the MSS ('Maximal Segment Size') to advertise to these destinations when estab‐
lishing TCP connections. If it is not given, Linux uses a default value calcu‐
lated from the first hop device MTU. (If the path to these destination is asym‐
metric, this guess may be wrong.)
Note that the default value is calculated from the first hop *device
MTU*, not the *route MTU*. In practice this is usually ok as long as the
other side of the tunnel has the mtu configured exactly the same, but we
should probably just set advmss correctly on these routes.
* Use golang.org/x/sys/unix for _linux.go sources
To support builds on GOARCH=386 and possibly elsewhere, it's necessary
to use the x/sys/unix package instead of the syscall package. This is
because the syscall package is frozen and does not support
SYS_GETSOCKNAME, SYS_RECVFROM, nor SYS_SENDTO for GOARCH=386.
This commit alone doesn't add support for 386 builds, just gets things
onto x/sys/unix so that it's possible.
The remaining uses of the syscall package relate to signals, which
cannot be switched to the x/sys/unix package at this time. Windows
support breaks, so they can either continue using the syscall package
(it's frozen, this is safe for Go 1.x at minimum), or something can be
written to just use both windows- and unix-compatible signals.
* Add linux-386, ppc64le targets to Makefile
Because 'linux' is linux-amd64 already, just add linux-386 and
linux-ppc64le targets to distinguish them. Would rename the linux
target but that might break existing uses.
Nathan Brown