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net/connstats: invert network logging data flow (#6272)

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Previously, tstun.Wrapper and magicsock.Conn managed their
own statistics data structure and relied on an external call to
Extract to extract (and reset) the statistics.
This makes it difficult to ensure a maximum size on the statistics
as the caller has no introspection into whether the number
of unique connections is getting too large.

Invert the control flow such that a *connstats.Statistics
is registered with tstun.Wrapper and magicsock.Conn.
Methods on non-nil *connstats.Statistics are called for every packet.
This allows the implementation of connstats.Statistics (in the future)
to better control when it needs to flush to ensure
bounds on maximum sizes.

The value registered into tstun.Wrapper and magicsock.Conn could
be an interface, but that has two performance detriments:

1. Method calls on interface values are more expensive since
they must go through a virtual method dispatch.

2. The implementation would need a sync.Mutex to protect the
statistics value instead of using an atomic.Pointer.

Given that methods on constats.Statistics are called for every packet,
we want reduce the CPU cost on this hot path.

Signed-off-by: Joe Tsai <joetsai@digital-static.net>
This commit is contained in:
Joe Tsai
2022-11-28 15:59:33 -08:00
committed by GitHub
parent 35c10373b5
commit 2e5d08ec4f
10 changed files with 172 additions and 252 deletions
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67
wgengine/magicsock/magicsock.go
View File

@@ -37,6 +37,7 @@ import (
"tailscale.com/health"
"tailscale.com/ipn/ipnstate"
"tailscale.com/logtail/backoff"
"tailscale.com/net/connstats"
"tailscale.com/net/dnscache"
"tailscale.com/net/interfaces"
"tailscale.com/net/netaddr"
@@ -52,7 +53,6 @@ import (
"tailscale.com/tstime/mono"
"tailscale.com/types/key"
"tailscale.com/types/logger"
"tailscale.com/types/netlogtype"
"tailscale.com/types/netmap"
"tailscale.com/types/nettype"
"tailscale.com/util/clientmetric"
@@ -337,19 +337,7 @@ type Conn struct {
port atomic.Uint32
// stats maintains per-connection counters.
// See SetStatisticsEnabled and ExtractStatistics for details.
stats struct {
enabled atomic.Bool
// TODO(joetsai): A per-Conn map of connections is easiest to implement.
// Since every packet occurs within the context of an endpoint,
// we could track the counts within the endpoint itself,
// and then merge the results when ExtractStatistics is called.
// That would avoid a map lookup for every packet.
mu sync.Mutex
m map[netlogtype.Connection]netlogtype.Counts
}
stats atomic.Pointer[connstats.Statistics]
// ============================================================
// mu guards all following fields; see userspaceEngine lock
@@ -1754,8 +1742,8 @@ func (c *Conn) receiveIP(b []byte, ipp netip.AddrPort, cache *ippEndpointCache,
ep = de
}
ep.noteRecvActivity()
if c.stats.enabled.Load() {
c.updateStats(ep.nodeAddr, ipp, netlogtype.Counts{RxPackets: 1, RxBytes: uint64(len(b))})
if stats := c.stats.Load(); stats != nil {
stats.UpdateRxPhysical(ep.nodeAddr, ipp, len(b))
}
return ep, true
}
@@ -1812,8 +1800,8 @@ func (c *Conn) processDERPReadResult(dm derpReadResult, b []byte) (n int, ep *en
}
ep.noteRecvActivity()
if c.stats.enabled.Load() {
c.updateStats(ep.nodeAddr, ipp, netlogtype.Counts{RxPackets: 1, RxBytes: uint64(dm.n)})
if stats := c.stats.Load(); stats != nil {
stats.UpdateRxPhysical(ep.nodeAddr, ipp, dm.n)
}
return n, ep
}
@@ -3306,37 +3294,10 @@ func (c *Conn) UpdateStatus(sb *ipnstate.StatusBuilder) {
})
}
// updateStats updates the statistics counters with the src, dst, and cnts.
// It is the caller's responsibility to check whether logging is enabled.
func (c *Conn) updateStats(src netip.Addr, dst netip.AddrPort, cnts netlogtype.Counts) {
conn := netlogtype.Connection{Src: netip.AddrPortFrom(src, 0), Dst: dst}
c.stats.mu.Lock()
defer c.stats.mu.Unlock()
mak.Set(&c.stats.m, conn, c.stats.m[conn].Add(cnts))
}
// SetStatisticsEnabled enables per-connection packet counters.
// Disabling statistics gathering does not reset the counters.
// ExtractStatistics must be called to reset the counters and
// be periodically called while enabled to avoid unbounded memory use.
func (c *Conn) SetStatisticsEnabled(enable bool) {
c.stats.enabled.Store(enable)
}
// ExtractStatistics extracts and resets the counters for all active connections.
// It must be called periodically otherwise the memory used is unbounded.
//
// The source is always a peer's tailscale IP address,
// while the destination is the peer's physical IP address and port.
// As a special case, packets routed through DERP use a destination address
// of 127.3.3.40 with the port being the DERP region.
// This node's tailscale IP address never appears in the returned map.
func (c *Conn) ExtractStatistics() map[netlogtype.Connection]netlogtype.Counts {
c.stats.mu.Lock()
defer c.stats.mu.Unlock()
m := c.stats.m
c.stats.m = nil
return m
// SetStatistics specifies a per-connection statistics aggregator.
// Nil may be specified to disable statistics gathering.
func (c *Conn) SetStatistics(stats *connstats.Statistics) {
c.stats.Store(stats)
}
func ippDebugString(ua netip.AddrPort) string {
@@ -3701,14 +3662,14 @@ func (de *endpoint) send(b []byte) error {
var err error
if udpAddr.IsValid() {
_, err = de.c.sendAddr(udpAddr, de.publicKey, b)
if err == nil && de.c.stats.enabled.Load() {
de.c.updateStats(de.nodeAddr, udpAddr, netlogtype.Counts{TxPackets: 1, TxBytes: uint64(len(b))})
if stats := de.c.stats.Load(); err == nil && stats != nil {
stats.UpdateTxPhysical(de.nodeAddr, udpAddr, len(b))
}
}
if derpAddr.IsValid() {
if ok, _ := de.c.sendAddr(derpAddr, de.publicKey, b); ok {
if de.c.stats.enabled.Load() {
de.c.updateStats(de.nodeAddr, derpAddr, netlogtype.Counts{TxPackets: 1, TxBytes: uint64(len(b))})
if stats := de.c.stats.Load(); stats != nil {
stats.UpdateTxPhysical(de.nodeAddr, derpAddr, len(b))
}
if err != nil {
// UDP failed but DERP worked, so good enough: