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envknob: support changing envknobs post-init

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Updates #5114

Change-Id: Ia423fc7486e1b3f3180a26308278be0086fae49b
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick
2022-09-14 12:49:39 -07:00
committed by Brad Fitzpatrick
parent 33ee2c058e
commit 74674b110d
31 changed files with 311 additions and 167 deletions
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26
net/dnscache/dnscache.go
View File

@ -141,7 +141,7 @@ func (r *Resolver) ttl() time.Duration {
return 10 * time.Minute
}
var debug = envknob.Bool("TS_DEBUG_DNS_CACHE")
var debug = envknob.RegisterBool("TS_DEBUG_DNS_CACHE")
// LookupIP returns the host's primary IP address (either IPv4 or
// IPv6, but preferring IPv4) and optionally its IPv6 address, if
@ -167,14 +167,14 @@ func (r *Resolver) LookupIP(ctx context.Context, host string) (ip, v6 netip.Addr
}
if ip, err := netip.ParseAddr(host); err == nil {
ip = ip.Unmap()
if debug {
if debug() {
log.Printf("dnscache: %q is an IP", host)
}
return ip, zaddr, []netip.Addr{ip}, nil
}
if ip, ip6, allIPs, ok := r.lookupIPCache(host); ok {
if debug {
if debug() {
log.Printf("dnscache: %q = %v (cached)", host, ip)
}
return ip, ip6, allIPs, nil
@ -192,13 +192,13 @@ func (r *Resolver) LookupIP(ctx context.Context, host string) (ip, v6 netip.Addr
if res.Err != nil {
if r.UseLastGood {
if ip, ip6, allIPs, ok := r.lookupIPCacheExpired(host); ok {
if debug {
if debug() {
log.Printf("dnscache: %q using %v after error", host, ip)
}
return ip, ip6, allIPs, nil
}
}
if debug {
if debug() {
log.Printf("dnscache: error resolving %q: %v", host, res.Err)
}
return zaddr, zaddr, nil, res.Err
@ -206,7 +206,7 @@ func (r *Resolver) LookupIP(ctx context.Context, host string) (ip, v6 netip.Addr
r := res.Val
return r.ip, r.ip6, r.allIPs, nil
case <-ctx.Done():
if debug {
if debug() {
log.Printf("dnscache: context done while resolving %q: %v", host, ctx.Err())
}
return zaddr, zaddr, nil, ctx.Err()
@ -250,7 +250,7 @@ func (r *Resolver) lookupTimeoutForHost(host string) time.Duration {
func (r *Resolver) lookupIP(host string) (ip, ip6 netip.Addr, allIPs []netip.Addr, err error) {
if ip, ip6, allIPs, ok := r.lookupIPCache(host); ok {
if debug {
if debug() {
log.Printf("dnscache: %q found in cache as %v", host, ip)
}
return ip, ip6, allIPs, nil
@ -300,13 +300,13 @@ func (r *Resolver) addIPCache(host string, ip, ip6 netip.Addr, allIPs []netip.Ad
if ip.IsPrivate() {
// Don't cache obviously wrong entries from captive portals.
// TODO: use DoH or DoT for the forwarding resolver?
if debug {
if debug() {
log.Printf("dnscache: %q resolved to private IP %v; using but not caching", host, ip)
}
return
}
if debug {
if debug() {
log.Printf("dnscache: %q resolved to IP %v; caching", host, ip)
}
@ -382,7 +382,7 @@ func (d *dialer) DialContext(ctx context.Context, network, address string) (retC
}
i4s := v4addrs(allIPs)
if len(i4s) < 2 {
if debug {
if debug() {
log.Printf("dnscache: dialing %s, %s for %s", network, ip, address)
}
c, err := dc.dialOne(ctx, ip.Unmap())
@ -406,7 +406,7 @@ func (d *dialer) shouldTryBootstrap(ctx context.Context, err error, dc *dialCall
// Can't try bootstrap DNS if we don't have a fallback function
if d.dnsCache.LookupIPFallback == nil {
if debug {
if debug() {
log.Printf("dnscache: not using bootstrap DNS: no fallback")
}
return false
@ -415,7 +415,7 @@ func (d *dialer) shouldTryBootstrap(ctx context.Context, err error, dc *dialCall
// We can't retry if the context is canceled, since any further
// operations with this context will fail.
if ctxErr := ctx.Err(); ctxErr != nil {
if debug {
if debug() {
log.Printf("dnscache: not using bootstrap DNS: context error: %v", ctxErr)
}
return false
@ -423,7 +423,7 @@ func (d *dialer) shouldTryBootstrap(ctx context.Context, err error, dc *dialCall
wasTrustworthy := dc.dnsWasTrustworthy()
if wasTrustworthy {
if debug {
if debug() {
log.Printf("dnscache: not using bootstrap DNS: DNS was trustworthy")
}
return false

6
net/dnscache/dnscache_test.go
View File

@ -167,10 +167,8 @@ func TestInterleaveSlices(t *testing.T) {
func TestShouldTryBootstrap(t *testing.T) {
oldDebug := debug
t.Cleanup(func() {
debug = oldDebug
})
debug = true
t.Cleanup(func() { debug = oldDebug })
debug = func() bool { return true }
type step struct {
ip netip.Addr // IP we pretended to dial