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wgengine/magicsock: fix data race regression in disco ping callbacks

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Regression from c15997511de3. The callback could be run multiple times
from different endpoints.

Fixes #9801

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2023-10-14 13:16:04 -07:00 committed by Brad Fitzpatrick
parent 5297bd2cff
commit a6270826a3
2 changed files with 33 additions and 21 deletions
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52
wgengine/magicsock/endpoint.go
View File

@ -105,9 +105,8 @@ type sentPing struct {
at mono.Time
timer *time.Timer // timeout timer
purpose discoPingPurpose
size int // size of the disco message
res *ipnstate.PingResult // nil unless CLI ping
cb func(*ipnstate.PingResult) // nil unless CLI ping
size int // size of the disco message
resCB *pingResultAndCallback // or nil for internal use
}
// endpointState is some state and history for a specific endpoint of
@ -431,7 +430,7 @@ func (de *endpoint) heartbeat() {
udpAddr, _, _ := de.addrForSendLocked(now)
if udpAddr.IsValid() {
// We have a preferred path. Ping that every 2 seconds.
de.startDiscoPingLocked(udpAddr, now, pingHeartbeat, 0, nil, nil)
de.startDiscoPingLocked(udpAddr, now, pingHeartbeat, 0, nil)
}
if de.wantFullPingLocked(now) {
@ -475,9 +474,20 @@ func (de *endpoint) noteActiveLocked() {
// can send - the maximum packet size minus the IPv4 and UDP headers.
var MaxDiscoPingSize = tstun.MaxPacketSize - 20 - 8
// cliPing starts a ping for the "tailscale ping" command. res is value to call cb with,
// already partially filled.
func (de *endpoint) cliPing(res *ipnstate.PingResult, size int, cb func(*ipnstate.PingResult)) {
type pingResultAndCallback struct {
taken atomic.Bool // first CompareAndSwamp from false to true takes ownership of res
res *ipnstate.PingResult
cb func(*ipnstate.PingResult)
}
func (p *pingResultAndCallback) reply() bool {
return p != nil && p.taken.CompareAndSwap(false, true)
}
// discoPing starts a disc-level ping for the "tailscale ping" command (or other
// callers, such as c2n). res is value to call cb with, already partially
// filled. cb must be called at most once. Once called, ownership of res passes to db.
func (de *endpoint) discoPing(res *ipnstate.PingResult, size int, cb func(*ipnstate.PingResult)) {
de.mu.Lock()
defer de.mu.Unlock()
@ -492,21 +502,23 @@ func (de *endpoint) cliPing(res *ipnstate.PingResult, size int, cb func(*ipnstat
return
}
resCB := &pingResultAndCallback{res: res, cb: cb}
now := mono.Now()
udpAddr, derpAddr := de.addrForPingSizeLocked(now, size)
if derpAddr.IsValid() {
de.startDiscoPingLocked(derpAddr, now, pingCLI, size, res, cb)
de.startDiscoPingLocked(derpAddr, now, pingCLI, size, resCB)
}
if udpAddr.IsValid() && now.Before(de.trustBestAddrUntil) {
// Already have an active session, so just ping the address we're using.
// Otherwise "tailscale ping" results to a node on the local network
// can look like they're bouncing between, say 10.0.0.0/9 and the peer's
// IPv6 address, both 1ms away, and it's random who replies first.
de.startDiscoPingLocked(udpAddr, now, pingCLI, size, res, cb)
de.startDiscoPingLocked(udpAddr, now, pingCLI, size, resCB)
} else {
for ep := range de.endpointState {
de.startDiscoPingLocked(ep, now, pingCLI, size, res, cb)
de.startDiscoPingLocked(ep, now, pingCLI, size, resCB)
}
}
de.noteActiveLocked()
@ -660,10 +672,11 @@ const (
pingCLI
)
// startDiscoPingLocked sends a disco ping to ep in a separate
// goroutine. res and cb are for returning the results of CLI pings,
// otherwise they are nil.
func (de *endpoint) startDiscoPingLocked(ep netip.AddrPort, now mono.Time, purpose discoPingPurpose, size int, res *ipnstate.PingResult, cb func(*ipnstate.PingResult)) {
// startDiscoPingLocked sends a disco ping to ep in a separate goroutine. resCB,
// if non-nil, means that a caller external to the magicsock package internals
// is interested in the result (such as a CLI "tailscale ping" or a c2n ping
// request, etc)
func (de *endpoint) startDiscoPingLocked(ep netip.AddrPort, now mono.Time, purpose discoPingPurpose, size int, resCB *pingResultAndCallback) {
if runtime.GOOS == "js" {
return
}
@ -710,8 +723,7 @@ func (de *endpoint) startDiscoPingLocked(ep netip.AddrPort, now mono.Time, purpo
at: now,
timer: time.AfterFunc(pingTimeoutDuration, func() { de.discoPingTimeout(txid) }),
purpose: purpose,
res: res,
cb: cb,
resCB: resCB,
size: s,
}
go de.sendDiscoPing(ep, epDisco.key, txid, s, logLevel)
@ -742,7 +754,7 @@ func (de *endpoint) sendDiscoPingsLocked(now mono.Time, sendCallMeMaybe bool) {
de.c.dlogf("[v1] magicsock: disco: send, starting discovery for %v (%v)", de.publicKey.ShortString(), de.discoShort())
}
de.startDiscoPingLocked(ep, now, pingDiscovery, 0, nil, nil)
de.startDiscoPingLocked(ep, now, pingDiscovery, 0, nil)
}
derpAddr := de.derpAddr
if sentAny && sendCallMeMaybe && derpAddr.IsValid() {
@ -1106,11 +1118,11 @@ func (de *endpoint) handlePongConnLocked(m *disco.Pong, di *discoInfo, src netip
}
// Currently only CLI ping uses this callback.
if sp.cb != nil {
if sp.resCB.reply() {
if sp.purpose == pingCLI {
de.c.populateCLIPingResponseLocked(sp.res, latency, sp.to)
de.c.populateCLIPingResponseLocked(sp.resCB.res, latency, sp.to)
}
go sp.cb(sp.res)
go sp.resCB.cb(sp.resCB.res)
}
// Promote this pong response to our current best address if it's lower latency.

2
wgengine/magicsock/magicsock.go
View File

@ -757,7 +757,7 @@ func (c *Conn) Ping(peer tailcfg.NodeView, res *ipnstate.PingResult, size int, c
cb(res)
return
}
ep.cliPing(res, size, cb)
ep.discoPing(res, size, cb)
}
// c.mu must be held