From 96dce1cb9fbe0014e14ca5f20f31db0f3eb3f21b Mon Sep 17 00:00:00 2001
From: Martynas Pumputis <m@lambda.lt>
Date: Tue, 2 Jun 2020 14:44:34 +0200
Subject: [PATCH] Add LinkIndex to Addr struct

Currently, it's cumbersome to get a link by an IP addr - one needs to
list all links and then call AddrList() for each of them.

Considering that ifindex is already available to to the parseAddr()
helper function, we can expose it to a user via the newly added
Addr.LinkIndex field. This makes the retrieving link by IP addr much
more simple.

Signed-off-by: Martynas Pumputis <m@lambda.lt>
---
 addr.go       |  1 +
 addr_linux.go | 14 +++++++-------
 addr_test.go  |  4 ++++
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/addr.go b/addr.go
index f08c956..653f540 100644
--- a/addr.go
+++ b/addr.go
@@ -17,6 +17,7 @@ type Addr struct {
 	Broadcast   net.IP
 	PreferedLft int
 	ValidLft    int
+	LinkIndex   int
 }
 
 // String returns $ip/$netmask $label
diff --git a/addr_linux.go b/addr_linux.go
index 1358bee..71da251 100644
--- a/addr_linux.go
+++ b/addr_linux.go
@@ -193,12 +193,12 @@ func (h *Handle) AddrList(link Link, family int) ([]Addr, error) {
 
 	var res []Addr
 	for _, m := range msgs {
-		addr, msgFamily, ifindex, err := parseAddr(m)
+		addr, msgFamily, err := parseAddr(m)
 		if err != nil {
 			return res, err
 		}
 
-		if link != nil && ifindex != indexFilter {
+		if link != nil && addr.LinkIndex != indexFilter {
 			// Ignore messages from other interfaces
 			continue
 		}
@@ -213,11 +213,11 @@ func (h *Handle) AddrList(link Link, family int) ([]Addr, error) {
 	return res, nil
 }
 
-func parseAddr(m []byte) (addr Addr, family, index int, err error) {
+func parseAddr(m []byte) (addr Addr, family int, err error) {
 	msg := nl.DeserializeIfAddrmsg(m)
 
 	family = -1
-	index = -1
+	addr.LinkIndex = -1
 
 	attrs, err1 := nl.ParseRouteAttr(m[msg.Len():])
 	if err1 != nil {
@@ -226,7 +226,7 @@ func parseAddr(m []byte) (addr Addr, family, index int, err error) {
 	}
 
 	family = int(msg.Family)
-	index = int(msg.Index)
+	addr.LinkIndex = int(msg.Index)
 
 	var local, dst *net.IPNet
 	for _, attr := range attrs {
@@ -391,7 +391,7 @@ func addrSubscribeAt(newNs, curNs netns.NsHandle, ch chan<- AddrUpdate, done <-c
 					continue
 				}
 
-				addr, _, ifindex, err := parseAddr(m.Data)
+				addr, _, err := parseAddr(m.Data)
 				if err != nil {
 					if cberr != nil {
 						cberr(fmt.Errorf("could not parse address: %v", err))
@@ -400,7 +400,7 @@ func addrSubscribeAt(newNs, curNs netns.NsHandle, ch chan<- AddrUpdate, done <-c
 				}
 
 				ch <- AddrUpdate{LinkAddress: *addr.IPNet,
-					LinkIndex:   ifindex,
+					LinkIndex:   addr.LinkIndex,
 					NewAddr:     msgType == unix.RTM_NEWADDR,
 					Flags:       addr.Flags,
 					Scope:       addr.Scope,
diff --git a/addr_test.go b/addr_test.go
index 4f4ec9e..eddf591 100644
--- a/addr_test.go
+++ b/addr_test.go
@@ -94,6 +94,10 @@ func DoTestAddr(t *testing.T, FunctionUndertest func(Link, *Addr) error) {
 			t.Fatalf("Address scope not set properly, got=%d, expected=%d", addrs[0].Scope, tt.expected.Scope)
 		}
 
+		if ifindex := link.Attrs().Index; ifindex != addrs[0].LinkIndex {
+			t.Fatalf("Address ifindex not set properly, got=%d, expected=%d", addrs[0].LinkIndex, ifindex)
+		}
+
 		if tt.expected.Peer != nil {
 			if !addrs[0].PeerEqual(*tt.expected) {
 				t.Fatalf("Peer Address ip no set properly, got=%s, expected=%s", addrs[0].Peer, tt.expected.Peer)