84 lines
2.9 KiB
Go
84 lines
2.9 KiB
Go
// Copyright 2018 Google LLC. All Rights Reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package nftables
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import (
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"encoding/binary"
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"net"
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"github.com/google/nftables/binaryutil"
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"golang.org/x/sys/unix"
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)
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func extraHeader(family uint8, resID uint16) []byte {
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return append([]byte{
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family,
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unix.NFNETLINK_V0,
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}, binaryutil.BigEndian.PutUint16(resID)...)
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}
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// General form of address family dependent message, see
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// https://git.netfilter.org/libnftnl/tree/include/linux/netfilter/nfnetlink.h#29
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type NFGenMsg struct {
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NFGenFamily uint8
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Version uint8
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ResourceID uint16
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}
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func (genmsg *NFGenMsg) Decode(b []byte) {
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if len(b) < 16 {
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return
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}
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genmsg.NFGenFamily = b[0]
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genmsg.Version = b[1]
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genmsg.ResourceID = binary.BigEndian.Uint16(b[2:])
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}
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// GetFirstAndLastIPFromCIDR returns the first and last IP address from a CIDR.
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func GetFirstAndLastIPFromCIDR(cidr string) (firstIP, lastIP net.IP, err error) {
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_, subnet, err := net.ParseCIDR(cidr)
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if err != nil {
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return nil, nil, err
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}
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firstIP = make(net.IP, len(subnet.IP))
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lastIP = make(net.IP, len(subnet.IP))
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switch len(subnet.IP) {
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case net.IPv4len:
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mask := binary.BigEndian.Uint32(subnet.Mask)
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ip := binary.BigEndian.Uint32(subnet.IP)
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// To achieve the first IP address, we need to AND the IP with the mask.
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// The AND operation will set all bits in the host part to 0.
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binary.BigEndian.PutUint32(firstIP, ip&mask)
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// To achieve the last IP address, we need to OR the IP network with the inverted mask.
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// The AND between the IP and the mask will set all bits in the host part to 0, keeping the network part.
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// The XOR between the mask and 0xffffffff will set all bits in the host part to 1, and the network part to 0.
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// The OR operation will keep the host part unchanged, and sets the host part to all 1.
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binary.BigEndian.PutUint32(lastIP, (ip&mask)|(mask^0xffffffff))
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case net.IPv6len:
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mask1 := binary.BigEndian.Uint64(subnet.Mask[:8])
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mask2 := binary.BigEndian.Uint64(subnet.Mask[8:])
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ip1 := binary.BigEndian.Uint64(subnet.IP[:8])
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ip2 := binary.BigEndian.Uint64(subnet.IP[8:])
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binary.BigEndian.PutUint64(firstIP[:8], ip1&mask1)
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binary.BigEndian.PutUint64(firstIP[8:], ip2&mask2)
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binary.BigEndian.PutUint64(lastIP[:8], (ip1&mask1)|(mask1^0xffffffffffffffff))
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binary.BigEndian.PutUint64(lastIP[8:], (ip2&mask2)|(mask2^0xffffffffffffffff))
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}
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return firstIP, lastIP, nil
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}
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