Add support for ignore-df flag in gretap links

Signed-off-by: Giuseppe Ognibene <ognibenegiuseppe8@gmail.com>

link.go

@@ -1118,8 +1118,16 @@ type Gretap struct {
 	EncapFlags uint16
 	Link       uint32
 	FlowBased  bool
+	IgnoreDf   GretapIgnoreDf
 }
 
+type GretapIgnoreDf uint8
+
+const (
+	GRETAP_IGNORE_DF_FALSE = iota
+	GRETAP_IGNORE_DF_TRUE
+)
+
 func (gretap *Gretap) Attrs() *LinkAttrs {
 	return &gretap.LinkAttrs
 }

link_linux.go

@@ -3461,6 +3461,9 @@ func addGretapAttrs(gretap *Gretap, linkInfo *nl.RtAttr) {
 	data.AddRtAttr(nl.IFLA_GRE_ENCAP_FLAGS, nl.Uint16Attr(gretap.EncapFlags))
 	data.AddRtAttr(nl.IFLA_GRE_ENCAP_SPORT, htons(gretap.EncapSport))
 	data.AddRtAttr(nl.IFLA_GRE_ENCAP_DPORT, htons(gretap.EncapDport))
+	if gretap.IgnoreDf != GRETAP_IGNORE_DF_FALSE {
+		data.AddRtAttr(nl.IFLA_GRE_IGNORE_DF, nl.Uint8Attr(uint8(gretap.IgnoreDf)))
+	}
 }
 
 func parseGretapData(link Link, data []syscall.NetlinkRouteAttr) {

nl/link_linux.go

@@ -274,6 +274,7 @@ const (
 	IFLA_GRE_ENCAP_SPORT
 	IFLA_GRE_ENCAP_DPORT
 	IFLA_GRE_COLLECT_METADATA
+	IFLA_GRE_IGNORE_DF
 	IFLA_GRE_MAX = IFLA_GRE_COLLECT_METADATA
 )