Remove bad suppress_prefixlength iproute2 rule

This change gives tun priority over DHCP 121 rules

Author: nekohasekai

tun_linux.go

@@ -581,7 +581,7 @@ func (t *NativeTun) rules() []*netlink.Rule {
 			it.Family = unix.AF_INET6
 			rules = append(rules, it)
 		}*/
-		if p4 {
+		if p4 && !t.options.StrictRoute {
 			it = netlink.NewRule()
 			it.Priority = priority
 			it.IPProto = syscall.IPPROTO_ICMP
@@ -590,7 +590,7 @@ func (t *NativeTun) rules() []*netlink.Rule {
 			rules = append(rules, it)
 			priority++
 		}
-		if p6 {
+		if p6 && !t.options.StrictRoute {
 			it = netlink.NewRule()
 			it.Priority = priority6
 			it.IPProto = syscall.IPPROTO_ICMPV6
@@ -599,26 +599,6 @@ func (t *NativeTun) rules() []*netlink.Rule {
 			rules = append(rules, it)
 			priority6++
 		}
-		if p4 {
-			it = netlink.NewRule()
-			it.Priority = priority
-			it.Invert = true
-			it.Dport = netlink.NewRulePortRange(53, 53)
-			it.Table = unix.RT_TABLE_MAIN
-			it.SuppressPrefixlen = 0
-			it.Family = unix.AF_INET
-			rules = append(rules, it)
-		}
-		if p6 {
-			it = netlink.NewRule()
-			it.Priority = priority6
-			it.Invert = true
-			it.Dport = netlink.NewRulePortRange(53, 53)
-			it.Table = unix.RT_TABLE_MAIN
-			it.SuppressPrefixlen = 0
-			it.Family = unix.AF_INET6
-			rules = append(rules, it)
-		}
 	}
 
 	if p4 {