On darwin an unconnected sendto runs the address and MAC policy checks
and the EndpointSecurity send check for every datagram, and while
xprotectd throttles it each send takes about 185us, which caps a
tunnel's upload and, through its ACKs, its download. A connected socket
runs those checks once, at connect, and it is the only UDP send that
reports the interface queue's flow control, as ENOBUFS.
Only the current direct remote of an established tunnel is eligible.
udp.EstablishedPeerConn is an optional Conn interface, implemented on
darwin; establishedRemotes refcounts remotes over the main hostmap and
tells each writer on the first and last reference: handshake completion
adds one, deleting or retiring a hostinfo removes it, SetRemote (roaming,
SetRemoteIfPreferred, control, ssh) moves it. Pending and relayed
hostinfos hold none, and a rehandshake's two hostinfos share one.
An eligible peer that Nebula sends NEBULA_CONNSOCK_RUN (64) datagrams to
within NEBULA_CONNSOCK_WINDOW (1s) gets a connected socket: SO_REUSEPORT,
bound to the source address the listener's route to the peer picks on
the listener's port, carrying the listener's IP_BOUND_IF. The peer sees
the same address and port as from the listener, and the socket's reader
delivers through the listener's reader. The listener itself never sets
SO_REUSEPORT (listen routines still do), so no other uid can bind the
port; with a specific listen.host and no routines connected sockets stay
off, since sharing an exact address needs SO_REUSEPORT on both.
All routines listening on one address share one set of connected
sockets: at most NEBULA_CONNSOCKS (8), one per peer, with opens from a
bucket that refills one per NEBULA_CONNSOCK_OPEN_EVERY (1s). A socket
closes when its peer stops being eligible, after NEBULA_CONNSOCK_IDLE
(30s) without traffic, on Rebind (of every routine) and Close, and on an
error that means the connected path is gone. Closing never runs under
the hostmap's or the eligibility lock; the peer can't reopen until the
close finishes. A send that gets ENOBUFS or EAGAIN waits within one
10ms budget shared by every writer since the last send that went
through, then drops; nothing waits in the netpoller without a deadline.
When nothing is eligible or open, a send costs one atomic load before
the listener path.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
remove runtime.LockOSThread() because it makes things worse now
remove the "custom" Write() method from tun_linux.go, the stdlib path via os.File performs better
We should change our guidance around number of routines, ~2 per thread (that you wish to use for Nebula) seems to be about right now
If the host OS is already big endian, we were swapping bytes when we
shouldn't have. Use the Go helper to make sure we do the endianness
correctly
Fixes: #1189
On some systems, IPv6 is disabled (for example, CIS benchmark recommends to disable it when not used), but currently all UDP connections are using AF_INET6 sockets.
When we are binding AF_INET6 socket to an address like ::ffff:1.2.3.4 (IPv4 addresses are parsed by net.ParseIP this way), we can't send or receive IPv6 packets anyway, so this will not break any scenarios.
---------
Co-authored-by: Wade Simmons <wsimmons@slack-corp.com>
* add calculated_remotes
This setting allows us to "guess" what the remote might be for a host
while we wait for the lighthouse response. For networks that hard
designed with in mind, it can help speed up handshake performance, as well as
improve resiliency in the case that all lighthouses are down.
Example:
lighthouse:
# ...
calculated_remotes:
# For any Nebula IPs in 10.0.10.0/24, this will apply the mask and add
# the calculated IP as an initial remote (while we wait for the response
# from the lighthouse). Both CIDRs must have the same mask size.
# For example, Nebula IP 10.0.10.123 will have a calculated remote of
# 192.168.1.123
10.0.10.0/24:
- mask: 192.168.1.0/24
port: 4242
* figure out what is up with this test
* add test
* better logic for sending handshakes
Keep track of the last light of hosts we sent handshakes to. Only log
handshake sent messages if the list has changed.
Remove the test Test_NewHandshakeManagerTrigger because it is faulty and
makes no sense. It relys on the fact that no handshake packets actually
get sent, but with these changes we would send packets now (which it
should!)
* use atomic.Pointer
* cleanup to make it clearer
* fix typo in example
