From 3156765985f2e7ad7b533c893de9d5ce56aab0ee Mon Sep 17 00:00:00 2001
From: Mitchell Riedstra <mitch@riedstra.dev>
Date: Wed, 11 Aug 2021 23:44:53 -0400
Subject: Add a Windows specific function to scrape the route table for the IP
 address from the default route.

---
 cmd/web/gethostip.go | 36 +++++++++++++++++++++++++
 cmd/web/util.go      | 33 -----------------------
 cmd/web/windows.go   | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 112 insertions(+), 33 deletions(-)
 create mode 100644 cmd/web/gethostip.go

diff --git a/cmd/web/gethostip.go b/cmd/web/gethostip.go
new file mode 100644
index 0000000..3788ac1
--- /dev/null
+++ b/cmd/web/gethostip.go
@@ -0,0 +1,36 @@
+// +build dragonfly freebsd linux nacl netbsd openbsd solaris darwin
+
+package main
+
+// GetHostIP attempts to guess the IP address of the current machine and
+// returns that. Simply bails at the first non sane looking IP and returns it.
+// Not ideal but it should work well enough most of the time
+func GetHostIP() string {
+	iFaces, err := net.Interfaces()
+	if err != nil {
+		return "127.0.0.1"
+	}
+
+	// RFC 3927
+	_, ipv4LinkLocal, _ := net.ParseCIDR("169.254.0.0/16")
+
+	for _, iFace := range iFaces {
+		addrs, err := iFace.Addrs()
+		if err != nil {
+			continue
+		}
+
+		for _, a := range addrs {
+			n, ok := a.(*net.IPNet)
+			if !ok {
+				continue
+			}
+
+			if n.IP.To4() != nil && !n.IP.IsLoopback() && !ipv4LinkLocal.Contains(n.IP.To4()) {
+				return n.IP.String()
+			}
+		}
+	}
+
+	return "127.0.0.1"
+}
diff --git a/cmd/web/util.go b/cmd/web/util.go
index 454912f..294079c 100644
--- a/cmd/web/util.go
+++ b/cmd/web/util.go
@@ -57,39 +57,6 @@ func getShareLink() string {
 	return fmt.Sprintf("http://%s:%s/", GetHostIP(), getPort())
 }
 
-// GetHostIP attempts to guess the IP address of the current machine and
-// returns that. Simply bails at the first non sane looking IP and returns it.
-// Not ideal but it should work well enough most of the time
-func GetHostIP() string {
-	iFaces, err := net.Interfaces()
-	if err != nil {
-		return "127.0.0.1"
-	}
-
-	// RFC 3927
-	_, ipv4LinkLocal, _ := net.ParseCIDR("169.254.0.0/16")
-
-	for _, iFace := range iFaces {
-		addrs, err := iFace.Addrs()
-		if err != nil {
-			continue
-		}
-
-		for _, a := range addrs {
-			n, ok := a.(*net.IPNet)
-			if !ok {
-				continue
-			}
-
-			if n.IP.To4() != nil && !n.IP.IsLoopback() && !ipv4LinkLocal.Contains(n.IP.To4()) {
-				return n.IP.String()
-			}
-		}
-	}
-
-	return "127.0.0.1"
-}
-
 func getPort() string {
 	s := strings.Split(Listen, ":")
 
diff --git a/cmd/web/windows.go b/cmd/web/windows.go
index 76491f1..d7e32d2 100644
--- a/cmd/web/windows.go
+++ b/cmd/web/windows.go
@@ -2,6 +2,16 @@
 
 package main
 
+import (
+	"bufio"
+	"bytes"
+	"errors"
+	"fmt"
+	"io"
+	"os/exec"
+	"regexp"
+)
+
 // DefaultLib path for the operating system in question
 var DefaultLib string = `C:\Program Files (x86)\Steam\steamapps`
 
@@ -10,3 +20,69 @@ var DefaultLib string = `C:\Program Files (x86)\Steam\steamapps`
 func BrowserCommand(url string) []string {
 	return []string{"cmd", "/c", "start", url}
 }
+
+func GetHostIP() string {
+	s, err := GetHostIPFromRoutes()
+	if err != nil {
+		panic(err)
+	}
+	return s
+}
+
+// GetHostIPFromRoutes is a terrible little function to scrape up the
+// information about the route table and return the IP address associated with
+// the default route
+func GetHostIPFromRoutes() (string, error) {
+	spaceRe := regexp.MustCompile("  *")
+
+	c := exec.Command("route", "print", "-4")
+
+	b, err := c.Output()
+	if err != nil {
+		return "", err
+	}
+
+	rdr := bufio.NewReader(bytes.NewBuffer(b))
+
+	net := false
+	for {
+		l, err := rdr.ReadBytes('\n')
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return "", err
+		}
+
+		fmt.Println(string(l))
+
+		if bytes.HasPrefix(l, []byte("Network Destination")) && !net {
+			net = true
+			continue
+		}
+
+		if net && bytes.HasPrefix(l, []byte("=")) {
+			break
+		}
+
+		if net == false {
+			continue
+		}
+
+		fmt.Println("Before: ", string(l))
+
+		l = spaceRe.ReplaceAll(l, []byte{' '})
+		l = bytes.TrimPrefix(l, []byte{' '})
+
+		fields := bytes.Split(l, []byte(" "))
+
+		if len(fields) < 5 {
+			return "", errors.New("Less than five fields")
+		}
+
+		if bytes.Equal(fields[0], []byte("0.0.0.0")) {
+			return string(fields[3]), nil
+		}
+	}
+
+	return "", errors.New("Unable to parse IP from route table")
+}
-- 
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