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netfilter.go
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netfilter.go
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package l3
import (
"github.com/juliengk/go-netfilter/iptables"
)
const (
iptTFILTER = "filter"
iptCINPUT = "INPUT"
iptCFORWARD = "FORWARD"
iptCOUTPUT = "OUTPUT"
)
//SetDefaultFWRules sets the DROP policy on input and output, allows forwarding
func (r *Router) SetDefaultFWRules() error {
ipt4, _ := iptables.New(4, false)
ipt6, _ := iptables.New(6, false)
ipts := []*iptables.IPTables{ipt4, ipt6}
//apply same rules for both ipv4 and ipv6
for _, ipt := range ipts {
// ipt.Policy(iptTFILTER, iptCINPUT, "DROP")
ipt.Policy(iptTFILTER, iptCFORWARD, "ACCEPT")
// ipt.Policy(iptTFILTER, iptCOUTPUT, "DROP")
//Allow any loopback
ipt.Append(iptTFILTER, iptCINPUT, "-i", "lo", "-j", "ACCEPT")
ipt.Append(iptTFILTER, iptCOUTPUT, "-o", "lo", "-j", "ACCEPT")
//Allow BGP outbound
ipt.Append(iptTFILTER, iptCOUTPUT, "-p", "tcp", "--dport", "179", "-m", "conntrack", "--ctstate", "NEW,ESTABLISHED", "-j", "ACCEPT")
ipt.Append(iptTFILTER, iptCINPUT, "-p", "tcp", "--sport", "179", "-m", "conntrack", "--ctstate", "ESTABLISHED", "-j", "ACCEPT")
//Allow DHCP packets in/out
ipt.Append(iptTFILTER, iptCINPUT, "-p", "udp", "--dport", "67:68", "--sport", "67:68", "-j", "ACCEPT")
ipt.Append(iptTFILTER, iptCOUTPUT, "-p", "udp", "--dport", "67:68", "--sport", "67:68", "-j", "ACCEPT")
//Block DHCP from public iface
ipt.Append(iptTFILTER, iptCINPUT, "-i", "eth0", "-p", "udp", "--dport", "67:68", "--sport", "67:68", "-j", "DROP")
}
return nil
}