README
¶
mem-resolver
memresolver is an in-memory golang resolver that allows to override current golang Lookup func literals
How to use it
Create your custom Lookup function, is it common to overwrite LookupIP, that is the one used by the Dialer so we can redirect custom domains, per example.
func myLookupIP(ctx context.Context, network, host string) ([]net.IP, error) {
// fqdn appends a dot
if "mycustom.mydomain" == strings.TrimSuffix(host, ".") {
return []net.IP{net.ParseIP("127.0.0.1")}, nil
}
return net.DefaultResolver.LookupIP(ctx, network, host)
}
Once we have our cusotm Lookup function we create a custom net.Resolver
f := &MemResolver{
LookupIP: myLookupIP,
}
// override lookupIP
resolver := NewMemoryResolver(f)
This custom resolver implements a Dial function that can be used to override the net.Dialer resolver.
tr := &http.Transport{
Proxy: http.ProxyFromEnvironment,
DialContext: (&net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: 30 * time.Second,
Resolver: resolver,
}).DialContext,
}
client := &http.Client{
Transport: tr,
}
Check example_test.go for a full example.
Documentation
¶
Index ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func NewMemoryResolver ¶
func NewMemoryResolver(r *MemResolver) *net.Resolver
MemoryResolver returns an in-memory resolver that can override golang Lookup functions.
Types ¶
type MemResolver ¶
type MemResolver struct {
LookupAddr func(ctx context.Context, addr string) (names []string, err error)
LookupCNAME func(ctx context.Context, host string) (cname string, err error)
LookupHost func(ctx context.Context, host string) (addrs []string, err error)
LookupIP func(ctx context.Context, network, host string) ([]net.IP, error)
LookupMX func(ctx context.Context, name string) ([]*net.MX, error)
LookupNS func(ctx context.Context, name string) ([]*net.NS, error)
LookupPort func(ctx context.Context, network, service string) (port int, err error)
LookupSRV func(ctx context.Context, service, proto, name string) (cname string, addrs []*net.SRV, err error)
LookupTXT func(ctx context.Context, name string) ([]string, error)
}
MemResolver implement an in memory resolver that receives DNS questions and executes the corresponding Lookup functions. If the corresponding Lookup function is not present, it uses the DefaultResolver ones.
func (*MemResolver) ProcessDNSRequest ¶
func (r *MemResolver) ProcessDNSRequest(id uint16, q dnsmessage.Question) []byte
ProcessDNSRequest implements dnsHandlerFunc so it can be used in a MemResolver transforming a DNS request to the corresponding Golang Lookup functions.
Source Files