systemd-resolved (#1)

* system-resolved implementation

README.md

@@ -139,3 +139,161 @@ if watchdog != nil {
     }()
 }
 ```
+
+## Resolved
+
+[![PkgGoDev](https://pkg.go.dev/badge/github.com/iguanesolutions/go-systemd/resolved/resolved)](https://pkg.go.dev/github.com/iguanesolutions/go-systemd/v5/resolved)
+
+This package is still under development and very experimental, do not use it in production.
+We started this package in order to go deep into the DNS world. So we are opened to any suggestions/contributions on this.
+DNS is not trivial at all so there can be some stuff that are not rfc compliant (like sorting addresses etc...).
+
+The resolved package features:
+ * Pure Go implementation of `org.freedesktop.resolve1` dbus interface
+ * Resolver type (which uses the underlying dbus interface) that tries to implement the same methods as `net.Resolver` from Go standard library
+ * Unit tests (make sure Go resolver and systemd-resolved query the same dns server)
+
+### Dbus
+
+The following example shows how to use the resolve1 dbus connection to resolve an host:
+
+```go
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"syscall"
+
+	"github.com/iguanesolutions/go-systemd/v5/resolved"
+)
+
+func main() {
+	c, err := resolved.NewConn()
+	if err != nil {
+		log.Fatal("ERROR: ", err)
+	}
+	ctx := context.Background()
+	addrs, canonical, flags, err := c.ResolveHostname(ctx, 0, "google.com", syscall.AF_UNSPEC, 0)
+	if err != nil {
+		log.Println("ERROR: ", err)
+	} else {
+		fmt.Println("Addresses: ", addrs)
+		fmt.Println("Canonical: ", canonical)
+		fmt.Println("OutputFlags: ", flags)
+	}
+	err = c.Close()
+	if err != nil {
+		log.Println("ERROR: ", err)
+	}
+}
+```
+
+Output:
+
+```output
+Addresses:  [{
+        IfIndex: 2,
+        Family:  2,
+        IP:      142.250.74.238,
+} {
+        IfIndex: 2,
+        Family:  10,
+        IP:      2a00:1450:4007:80b::200e,
+}]
+Canonical:  google.com
+Flags:  1
+```
+
+### Resolver
+
+The following example shows how to use the resolved Resolver to resolve an host:
+
+```go
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+
+	"github.com/iguanesolutions/go-systemd/v5/resolved"
+)
+
+func main() {
+	r, err := resolved.NewResolver()
+	if err != nil {
+		log.Fatal("ERROR: ", err)
+	}
+	ctx := context.Background()
+	addrs, err := r.LookupHost(ctx, "google.com")
+	if err != nil {
+		log.Println("ERROR: ", err)
+	} else {
+		fmt.Println("Addresses: ", addrs)
+	}
+	err = r.Close()
+	if err != nil {
+		log.Println("ERROR: ", err)
+	}
+}
+```
+
+Output:
+
+```output
+Addresses:  [2a00:1450:4007:80b::200e 142.250.74.238]
+```
+
+### HTTP Client
+
+The following example shows how to use the systemd-resolved Resolver with the Go http client from the standard library:
+
+```go
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+
+	"github.com/iguanesolutions/go-systemd/v5/resolved"
+)
+
+func main() {
+	r, err := resolved.NewResolver()
+	if err != nil {
+		log.Fatal("ERROR: ", err)
+	}
+	// if you want to make a custom http client using systemd-resolved as resolver
+	httpCli := &http.Client{
+		Transport: &http.Transport{
+			DialContext: r.DialContext,
+		},
+	}
+	// or if you don't have an http client you can call HTTPClient method on resolver
+	// it comes with some nice default values.
+	httpCli = r.HTTPClient()
+	resp, err := httpCli.Get("https://google.com")
+	if err != nil {
+		log.Println("ERROR: ", err)
+	} else {
+		fmt.Println("Status: ", resp.Status)
+		err = resp.Body.Close()
+		if err != nil {
+			log.Println("ERROR: ", err)
+		}
+	}
+	err = r.Close()
+	if err != nil {
+		log.Println("ERROR: ", err)
+	}
+}
+```
+
+Output:
+
+```output
+Status:  200 OK
+```

go.mod

@@ -1,3 +1,9 @@
 module github.com/iguanesolutions/go-systemd/v5
 
 go 1.13
+
+require (
+	github.com/godbus/dbus/v5 v5.0.4
+	github.com/miekg/dns v1.1.42
+	golang.org/x/net v0.0.0-20210525063256-abc453219eb5
+)

go.sum

@@ -0,0 +1,18 @@
+github.com/godbus/dbus/v5 v5.0.4 h1:9349emZab16e7zQvpmsbtjc18ykshndd8y2PG3sgJbA=
+github.com/godbus/dbus/v5 v5.0.4/go.mod h1:xhWf0FNVPg57R7Z0UbKHbJfkEywrmjJnf7w5xrFpKfA=
+github.com/miekg/dns v1.1.42 h1:gWGe42RGaIqXQZ+r3WUGEKBEtvPHY2SXo4dqixDNxuY=
+github.com/miekg/dns v1.1.42/go.mod h1:+evo5L0630/F6ca/Z9+GAqzhjGyn8/c+TBaOyfEl0V4=
+golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
+golang.org/x/net v0.0.0-20210525063256-abc453219eb5 h1:wjuX4b5yYQnEQHzd+CBcrcC6OVR2J1CN6mUy0oSxIPo=
+golang.org/x/net v0.0.0-20210525063256-abc453219eb5/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
+golang.org/x/sync v0.0.0-20210220032951-036812b2e83c h1:5KslGYwFpkhGh+Q16bwMP3cOontH8FOep7tGV86Y7SQ=
+golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
+golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210303074136-134d130e1a04/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20210423082822-04245dca01da h1:b3NXsE2LusjYGGjL5bxEVZZORm/YEFFrWFjR8eFrw/c=
+golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
+golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/text v0.3.6 h1:aRYxNxv6iGQlyVaZmk6ZgYEDa+Jg18DxebPSrd6bg1M=
+golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=