net: respect go vs cgo resolver selection in all lookup routines
This is especially important for LookupAddr, which used to be pure Go
(lightweight, one goroutine per call) and without this CL is now
unconditionally cgo (heavy, one thread per call).
Fixes #12190.
Change-Id: I43436a942bc1838b024225893e156f280a1e80cf
Reviewed-on: https://go-review.googlesource.com/13698
Reviewed-by: Rob Pike <r@golang.org>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/net/conf.go b/src/net/conf.go
index 01bb585..c92e579 100644
--- a/src/net/conf.go
+++ b/src/net/conf.go
@@ -19,7 +19,7 @@
// forceCgoLookupHost forces CGO to always be used, if available.
forceCgoLookupHost bool
- netGo bool // "netgo" build tag in use (or no cgo)
+ netGo bool // go DNS resolution forced
netCgo bool // cgo DNS resolution forced
// machine has an /etc/mdns.allow file
@@ -112,6 +112,12 @@
}
}
+// canUseCgo reports whether calling cgo functions is allowed
+// for non-hostname lookups.
+func (c *conf) canUseCgo() bool {
+ return c.hostLookupOrder("") == hostLookupCgo
+}
+
// hostLookupOrder determines which strategy to use to resolve hostname.
func (c *conf) hostLookupOrder(hostname string) (ret hostLookupOrder) {
if c.dnsDebugLevel > 1 {
diff --git a/src/net/lookup_unix.go b/src/net/lookup_unix.go
index 1c811d2..a64da8b 100644
--- a/src/net/lookup_unix.go
+++ b/src/net/lookup_unix.go
@@ -74,19 +74,21 @@
}
func lookupPort(network, service string) (int, error) {
- port, err, ok := cgoLookupPort(network, service)
- if !ok {
- port, err = goLookupPort(network, service)
+ if systemConf().canUseCgo() {
+ if port, err, ok := cgoLookupPort(network, service); ok {
+ return port, err
+ }
}
- return port, err
+ return goLookupPort(network, service)
}
func lookupCNAME(name string) (string, error) {
- cname, err, ok := cgoLookupCNAME(name)
- if !ok {
- cname, err = goLookupCNAME(name)
+ if systemConf().canUseCgo() {
+ if cname, err, ok := cgoLookupCNAME(name); ok {
+ return cname, err
+ }
}
- return cname, err
+ return goLookupCNAME(name)
}
func lookupSRV(service, proto, name string) (string, []*SRV, error) {
@@ -148,9 +150,10 @@
}
func lookupAddr(addr string) ([]string, error) {
- ptrs, err, ok := cgoLookupPTR(addr)
- if !ok {
- ptrs, err = goLookupPTR(addr)
+ if systemConf().canUseCgo() {
+ if ptrs, err, ok := cgoLookupPTR(addr); ok {
+ return ptrs, err
+ }
}
- return ptrs, err
+ return goLookupPTR(addr)
}
