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net: centralize resolver selection logic

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This change removes the per GOOS hostLookupOrder wrappers.
passes the correct hostname to hostLookupOrder (windows,
plan9), so that the netdns+2 GODEBUG doesn't show empty
hostnames.

Uses the mustUseGoResolver instead of hostLookupOrder,
hostLookupOrder should only be used for hostname resolution,
not for lookups that do only DNS.

Change-Id: I18bbff06957910ae25c2bc78dfa9a46da76529fd
GitHub-Last-Rev: a27545dc25
GitHub-Pull-Request: golang/go#61525
Reviewed-on: https://go-review.googlesource.com/c/go/+/512215
Auto-Submit: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Run-TryBot: Mateusz Poliwczak <mpoliwczak34@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Mateusz Poliwczak 2023-08-26 16:43:17 +00:00 committed by Gopher Robot
parent ff00fdfdbe
commit 071aed2aaa
5 changed files with 38 additions and 53 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

19
src/net/conf.go
View File

@ -185,7 +185,24 @@ func goosPrefersCgo() bool {
// required to use the go resolver. The provided Resolver is optional. // required to use the go resolver. The provided Resolver is optional.
// This will report true if the cgo resolver is not available. // This will report true if the cgo resolver is not available.
func (c *conf) mustUseGoResolver(r *Resolver) bool { func (c *conf) mustUseGoResolver(r *Resolver) bool {
return c.netGo || r.preferGo() || !cgoAvailable if !cgoAvailable {
return true
}
if runtime.GOOS == "plan9" {
// TODO(bradfitz): for now we only permit use of the PreferGo
// implementation when there's a non-nil Resolver with a
// non-nil Dialer. This is a sign that they the code is trying
// to use their DNS-speaking net.Conn (such as an in-memory
// DNS cache) and they don't want to actually hit the network.
// Once we add support for looking the default DNS servers
// from plan9, though, then we can relax this.
if r == nil || r.Dial == nil {
return false
}
}
return c.netGo || r.preferGo()
} }
// addrLookupOrder determines which strategy to use to resolve addresses. // addrLookupOrder determines which strategy to use to resolve addresses.

3
src/net/dnsclient_unix.go
View File

@ -606,8 +606,7 @@ func goLookupIPFiles(name string) (addrs []IPAddr, canonical string) {
// goLookupIP is the native Go implementation of LookupIP. // goLookupIP is the native Go implementation of LookupIP.
// The libc versions are in cgo_*.go. // The libc versions are in cgo_*.go.
func (r *Resolver) goLookupIP(ctx context.Context, network, host string) (addrs []IPAddr, err error) { func (r *Resolver) goLookupIP(ctx context.Context, network, host string, order hostLookupOrder, conf *dnsConfig) (addrs []IPAddr, err error) {
order, conf := systemConf().hostLookupOrder(r, host)
addrs, _, err = r.goLookupIPCNAMEOrder(ctx, network, host, order, conf) addrs, _, err = r.goLookupIPCNAMEOrder(ctx, network, host, order, conf)
return return
} }

38
src/net/lookup_plan9.go
View File

@ -184,31 +184,11 @@ loop:
return return
} }
// preferGoOverPlan9 reports whether the resolver should use the
// "PreferGo" implementation rather than asking plan9 services
// for the answers.
func (r *Resolver) preferGoOverPlan9() bool {
_, _, res := r.preferGoOverPlan9WithOrderAndConf()
return res
}
func (r *Resolver) preferGoOverPlan9WithOrderAndConf() (hostLookupOrder, *dnsConfig, bool) {
order, conf := systemConf().hostLookupOrder(r, "") // name is unused
// TODO(bradfitz): for now we only permit use of the PreferGo
// implementation when there's a non-nil Resolver with a
// non-nil Dialer. This is a sign that they the code is trying
// to use their DNS-speaking net.Conn (such as an in-memory
// DNS cache) and they don't want to actually hit the network.
// Once we add support for looking the default DNS servers
// from plan9, though, then we can relax this.
return order, conf, order != hostLookupCgo && r != nil && r.Dial != nil
}
func (r *Resolver) lookupIP(ctx context.Context, network, host string) (addrs []IPAddr, err error) { func (r *Resolver) lookupIP(ctx context.Context, network, host string) (addrs []IPAddr, err error) {
if r.preferGoOverPlan9() { if order, conf := systemConf().hostLookupOrder(r, host); order != hostLookupCgo {
return r.goLookupIP(ctx, network, host) return r.goLookupIP(ctx, network, host, order, conf)
} }
lits, err := r.lookupHost(ctx, host) lits, err := r.lookupHost(ctx, host)
if err != nil { if err != nil {
return return
@ -253,7 +233,7 @@ func (*Resolver) lookupPort(ctx context.Context, network, service string) (port
} }
func (r *Resolver) lookupCNAME(ctx context.Context, name string) (cname string, err error) { func (r *Resolver) lookupCNAME(ctx context.Context, name string) (cname string, err error) {
if order, conf, preferGo := r.preferGoOverPlan9WithOrderAndConf(); preferGo { if order, conf := systemConf().hostLookupOrder(r, name); order != hostLookupCgo {
return r.goLookupCNAME(ctx, name, order, conf) return r.goLookupCNAME(ctx, name, order, conf)
} }
@ -274,7 +254,7 @@ func (r *Resolver) lookupCNAME(ctx context.Context, name string) (cname string,
} }
func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error) { func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (cname string, addrs []*SRV, err error) {
if r.preferGoOverPlan9() { if systemConf().mustUseGoResolver(r) {
return r.goLookupSRV(ctx, service, proto, name) return r.goLookupSRV(ctx, service, proto, name)
} }
var target string var target string
@ -306,7 +286,7 @@ func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (
} }
func (r *Resolver) lookupMX(ctx context.Context, name string) (mx []*MX, err error) { func (r *Resolver) lookupMX(ctx context.Context, name string) (mx []*MX, err error) {
if r.preferGoOverPlan9() { if systemConf().mustUseGoResolver(r) {
return r.goLookupMX(ctx, name) return r.goLookupMX(ctx, name)
} }
lines, err := queryDNS(ctx, name, "mx") lines, err := queryDNS(ctx, name, "mx")
@ -327,7 +307,7 @@ func (r *Resolver) lookupMX(ctx context.Context, name string) (mx []*MX, err err
} }
func (r *Resolver) lookupNS(ctx context.Context, name string) (ns []*NS, err error) { func (r *Resolver) lookupNS(ctx context.Context, name string) (ns []*NS, err error) {
if r.preferGoOverPlan9() { if systemConf().mustUseGoResolver(r) {
return r.goLookupNS(ctx, name) return r.goLookupNS(ctx, name)
} }
lines, err := queryDNS(ctx, name, "ns") lines, err := queryDNS(ctx, name, "ns")
@ -345,7 +325,7 @@ func (r *Resolver) lookupNS(ctx context.Context, name string) (ns []*NS, err err
} }
func (r *Resolver) lookupTXT(ctx context.Context, name string) (txt []string, err error) { func (r *Resolver) lookupTXT(ctx context.Context, name string) (txt []string, err error) {
if r.preferGoOverPlan9() { if systemConf().mustUseGoResolver(r) {
return r.goLookupTXT(ctx, name) return r.goLookupTXT(ctx, name)
} }
lines, err := queryDNS(ctx, name, "txt") lines, err := queryDNS(ctx, name, "txt")
@ -361,7 +341,7 @@ func (r *Resolver) lookupTXT(ctx context.Context, name string) (txt []string, er
} }
func (r *Resolver) lookupAddr(ctx context.Context, addr string) (name []string, err error) { func (r *Resolver) lookupAddr(ctx context.Context, addr string) (name []string, err error) {
if order, conf, preferGo := r.preferGoOverPlan9WithOrderAndConf(); preferGo { if order, conf := systemConf().addrLookupOrder(r, addr); order != hostLookupCgo {
return r.goLookupPTR(ctx, addr, order, conf) return r.goLookupPTR(ctx, addr, order, conf)
} }
arpa, err := reverseaddr(addr) arpa, err := reverseaddr(addr)

3
src/net/lookup_unix.go
View File

@ -62,9 +62,6 @@ func (r *Resolver) lookupHost(ctx context.Context, host string) (addrs []string,
} }
func (r *Resolver) lookupIP(ctx context.Context, network, host string) (addrs []IPAddr, err error) { func (r *Resolver) lookupIP(ctx context.Context, network, host string) (addrs []IPAddr, err error) {
if r.preferGo() {
return r.goLookupIP(ctx, network, host)
}
order, conf := systemConf().hostLookupOrder(r, host) order, conf := systemConf().hostLookupOrder(r, host)
if order == hostLookupCgo { if order == hostLookupCgo {
return cgoLookupIP(ctx, network, host) return cgoLookupIP(ctx, network, host)

28
src/net/lookup_windows.go
View File

@ -91,19 +91,11 @@ func (r *Resolver) lookupHost(ctx context.Context, name string) ([]string, error
return addrs, nil return addrs, nil
} }
// preferGoOverWindows reports whether the resolver should use the
// pure Go implementation rather than making win32 calls to ask the
// kernel for its answer.
func (r *Resolver) preferGoOverWindows() bool {
conf := systemConf()
order, _ := conf.hostLookupOrder(r, "") // name is unused
return order != hostLookupCgo
}
func (r *Resolver) lookupIP(ctx context.Context, network, name string) ([]IPAddr, error) { func (r *Resolver) lookupIP(ctx context.Context, network, name string) ([]IPAddr, error) {
if r.preferGoOverWindows() { if order, conf := systemConf().hostLookupOrder(r, name); order != hostLookupCgo {
return r.goLookupIP(ctx, network, name) return r.goLookupIP(ctx, network, name, order, conf)
} }
// TODO(bradfitz,brainman): use ctx more. See TODO below. // TODO(bradfitz,brainman): use ctx more. See TODO below.
var family int32 = syscall.AF_UNSPEC var family int32 = syscall.AF_UNSPEC
@ -200,7 +192,7 @@ func (r *Resolver) lookupIP(ctx context.Context, network, name string) ([]IPAddr
} }
func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int, error) { func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int, error) {
if r.preferGoOverWindows() { if systemConf().mustUseGoResolver(r) {
return lookupPortMap(network, service) return lookupPortMap(network, service)
} }
@ -249,7 +241,7 @@ func (r *Resolver) lookupPort(ctx context.Context, network, service string) (int
} }
func (r *Resolver) lookupCNAME(ctx context.Context, name string) (string, error) { func (r *Resolver) lookupCNAME(ctx context.Context, name string) (string, error) {
if order, conf := systemConf().hostLookupOrder(r, ""); order != hostLookupCgo { if order, conf := systemConf().hostLookupOrder(r, name); order != hostLookupCgo {
return r.goLookupCNAME(ctx, name, order, conf) return r.goLookupCNAME(ctx, name, order, conf)
} }
@ -274,7 +266,7 @@ func (r *Resolver) lookupCNAME(ctx context.Context, name string) (string, error)
} }
func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) { func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (string, []*SRV, error) {
if r.preferGoOverWindows() { if systemConf().mustUseGoResolver(r) {
return r.goLookupSRV(ctx, service, proto, name) return r.goLookupSRV(ctx, service, proto, name)
} }
// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this. // TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
@ -303,7 +295,7 @@ func (r *Resolver) lookupSRV(ctx context.Context, service, proto, name string) (
} }
func (r *Resolver) lookupMX(ctx context.Context, name string) ([]*MX, error) { func (r *Resolver) lookupMX(ctx context.Context, name string) ([]*MX, error) {
if r.preferGoOverWindows() { if systemConf().mustUseGoResolver(r) {
return r.goLookupMX(ctx, name) return r.goLookupMX(ctx, name)
} }
// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this. // TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
@ -326,7 +318,7 @@ func (r *Resolver) lookupMX(ctx context.Context, name string) ([]*MX, error) {
} }
func (r *Resolver) lookupNS(ctx context.Context, name string) ([]*NS, error) { func (r *Resolver) lookupNS(ctx context.Context, name string) ([]*NS, error) {
if r.preferGoOverWindows() { if systemConf().mustUseGoResolver(r) {
return r.goLookupNS(ctx, name) return r.goLookupNS(ctx, name)
} }
// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this. // TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
@ -348,7 +340,7 @@ func (r *Resolver) lookupNS(ctx context.Context, name string) ([]*NS, error) {
} }
func (r *Resolver) lookupTXT(ctx context.Context, name string) ([]string, error) { func (r *Resolver) lookupTXT(ctx context.Context, name string) ([]string, error) {
if r.preferGoOverWindows() { if systemConf().mustUseGoResolver(r) {
return r.goLookupTXT(ctx, name) return r.goLookupTXT(ctx, name)
} }
// TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this. // TODO(bradfitz): finish ctx plumbing. Nothing currently depends on this.
@ -374,7 +366,7 @@ func (r *Resolver) lookupTXT(ctx context.Context, name string) ([]string, error)
} }
func (r *Resolver) lookupAddr(ctx context.Context, addr string) ([]string, error) { func (r *Resolver) lookupAddr(ctx context.Context, addr string) ([]string, error) {
if order, conf := systemConf().hostLookupOrder(r, ""); order != hostLookupCgo { if order, conf := systemConf().addrLookupOrder(r, addr); order != hostLookupCgo {
return r.goLookupPTR(ctx, addr, order, conf) return r.goLookupPTR(ctx, addr, order, conf)
} }