diff options
Diffstat (limited to 'dhcpv4/nclient4/conn_linux.go')
| -rw-r--r-- | dhcpv4/nclient4/conn_linux.go | 13 |
1 files changed, 8 insertions, 5 deletions
diff --git a/dhcpv4/nclient4/conn_linux.go b/dhcpv4/nclient4/conn_linux.go index 00c8a32..d6edc38 100644 --- a/dhcpv4/nclient4/conn_linux.go +++ b/dhcpv4/nclient4/conn_linux.go @@ -115,11 +115,11 @@ func udpMatch(addr *net.UDPAddr, bound *net.UDPAddr) bool { // ReadFrom reads raw IP packets and will try to match them against // upc.boundAddr. Any matching packets are returned via the given buffer. func (upc *BroadcastRawUDPConn) ReadFrom(b []byte) (int, net.Addr, error) { - ipLen := IPv4MaximumHeaderSize - udpLen := UDPMinimumSize + ipHdrMaxLen := IPv4MaximumHeaderSize + udpHdrLen := UDPMinimumSize for { - pkt := make([]byte, ipLen+udpLen+len(b)) + pkt := make([]byte, ipHdrMaxLen+udpHdrLen+len(b)) n, _, err := upc.PacketConn.ReadFrom(pkt) if err != nil { return 0, nil, err @@ -137,7 +137,7 @@ func (upc *BroadcastRawUDPConn) ReadFrom(b []byte) (int, net.Addr, error) { if ipHdr.TransportProtocol() != UDPProtocolNumber { continue } - udpHdr := UDP(buf.Consume(udpLen)) + udpHdr := UDP(buf.Consume(udpHdrLen)) addr := &net.UDPAddr{ IP: net.IP(ipHdr.DestinationAddress()), @@ -150,7 +150,10 @@ func (upc *BroadcastRawUDPConn) ReadFrom(b []byte) (int, net.Addr, error) { IP: net.IP(ipHdr.SourceAddress()), Port: int(udpHdr.SourcePort()), } - return copy(b, buf.ReadAll()), srcAddr, nil + // Extra padding after end of IP packet should be ignored, + // if not dhcp option parsing will fail. + dhcpLen := int(ipHdr.PayloadLength()) - udpHdrLen + return copy(b, buf.Consume(dhcpLen)), srcAddr, nil } } |