feat templater: Add IP lookup function

This introduces support for looking up IP addresses using local DNS resolver.

Function will return a list of all IP addresses associated with hostname.
Further processing can be achieved using supported list template functions.

1 files changed, 34 insertions, 0 deletions

diff --git a/templater/dns.go b/templater/dns.go
new file mode 100644
index 000000000000..087399202b0c
--- /dev/null
+++ b/templater/dns.go
@@ -0,0 +1,34 @@
+// This file contains the implementation of a template function for retrieving IP addresses from DNS
+package templater
+
+import (
+	"fmt"
+	"github.com/polydawn/meep"
+	"net"
+	"os"
+)
+
+type DNSError struct {
+	meep.TraitAutodescribing
+	meep.TraitCausable
+	Output string
+}
+
+func GetIPsFromDNS(host string) ([]interface{}, error) {
+	fmt.Fprintf(os.Stderr, "Attempting to look up IP for %s in DNS\n", host)
+	ips, err := net.LookupIP(host)
+
+	if err != nil {
+		return nil, meep.New(
+			&DNSError{Output: "IP address lookup failed"},
+			meep.Cause(err),
+		)
+	}
+
+	var result []interface{} = make([]interface{}, len(ips))
+	for i, ip := range ips {
+		result[i] = ip
+	}
+
+	return result, nil
+}