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wgengine/magicsock: make endpoint.bestAddr Geneve-aware (#16195)

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This commit adds a new type to magicsock, epAddr, which largely ends up
replacing netip.AddrPort in packet I/O paths throughout, enabling
Geneve encapsulation over UDP awareness.

The conn.ReceiveFunc for UDP has been revamped to fix and more clearly
distinguish the different classes of packets we expect to receive: naked
STUN binding messages, naked disco, naked WireGuard, Geneve-encapsulated
disco, and Geneve-encapsulated WireGuard.

Prior to this commit, STUN matching logic in the RX path could swallow
a naked WireGuard packet if the keypair index, which is randomly
generated, happened to overlap with a subset of the STUN magic cookie.

Updates tailscale/corp#27502
Updates tailscale/corp#29326

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited
2025-06-06 09:46:29 -07:00
committed by GitHub
parent 3f7a9f82e3
commit 66ae8737f4
14 changed files with 604 additions and 386 deletions
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44
wgengine/magicsock/batching_conn_linux.go
View File

@@ -22,6 +22,7 @@ import (
"golang.org/x/sys/unix"
"tailscale.com/hostinfo"
"tailscale.com/net/neterror"
"tailscale.com/net/packet"
"tailscale.com/types/nettype"
)
@@ -92,9 +93,14 @@ const (
maxIPv6PayloadLen = 1<<16 - 1 - 8
)
// coalesceMessages iterates msgs, coalescing them where possible while
// maintaining datagram order. All msgs have their Addr field set to addr.
func (c *linuxBatchingConn) coalesceMessages(addr *net.UDPAddr, buffs [][]byte, msgs []ipv6.Message, offset int) int {
// coalesceMessages iterates 'buffs', setting and coalescing them in 'msgs'
// where possible while maintaining datagram order.
//
// All msgs have their Addr field set to addr.
//
// All msgs[i].Buffers[0] are preceded by a Geneve header with vni.get() if
// vni.isSet().
func (c *linuxBatchingConn) coalesceMessages(addr *net.UDPAddr, vni virtualNetworkID, buffs [][]byte, msgs []ipv6.Message, offset int) int {
var (
base = -1 // index of msg we are currently coalescing into
gsoSize int // segmentation size of msgs[base]
@@ -105,8 +111,17 @@ func (c *linuxBatchingConn) coalesceMessages(addr *net.UDPAddr, buffs [][]byte,
if addr.IP.To4() == nil {
maxPayloadLen = maxIPv6PayloadLen
}
vniIsSet := vni.isSet()
var gh packet.GeneveHeader
if vniIsSet {
gh.VNI = vni.get()
}
for i, buff := range buffs {
buff = buff[offset:]
if vniIsSet {
gh.Encode(buffs[i])
} else {
buff = buff[offset:]
}
if i > 0 {
msgLen := len(buff)
baseLenBefore := len(msgs[base].Buffers[0])
@@ -163,28 +178,37 @@ func (c *linuxBatchingConn) putSendBatch(batch *sendBatch) {
c.sendBatchPool.Put(batch)
}
func (c *linuxBatchingConn) WriteBatchTo(buffs [][]byte, addr netip.AddrPort, offset int) error {
func (c *linuxBatchingConn) WriteBatchTo(buffs [][]byte, addr epAddr, offset int) error {
batch := c.getSendBatch()
defer c.putSendBatch(batch)
if addr.Addr().Is6() {
as16 := addr.Addr().As16()
if addr.ap.Addr().Is6() {
as16 := addr.ap.Addr().As16()
copy(batch.ua.IP, as16[:])
batch.ua.IP = batch.ua.IP[:16]
} else {
as4 := addr.Addr().As4()
as4 := addr.ap.Addr().As4()
copy(batch.ua.IP, as4[:])
batch.ua.IP = batch.ua.IP[:4]
}
batch.ua.Port = int(addr.Port())
batch.ua.Port = int(addr.ap.Port())
var (
n int
retried bool
)
retry:
if c.txOffload.Load() {
n = c.coalesceMessages(batch.ua, buffs, batch.msgs, offset)
n = c.coalesceMessages(batch.ua, addr.vni, buffs, batch.msgs, offset)
} else {
vniIsSet := addr.vni.isSet()
var gh packet.GeneveHeader
if vniIsSet {
gh.VNI = addr.vni.get()
offset -= packet.GeneveFixedHeaderLength
}
for i := range buffs {
if vniIsSet {
gh.Encode(buffs[i])
}
batch.msgs[i].Buffers[0] = buffs[i][offset:]
batch.msgs[i].Addr = batch.ua
batch.msgs[i].OOB = batch.msgs[i].OOB[:0]