Commit 1c87ae05 authored May 22, 2013 by Ajay Dudani Committed by Vineeta Srivastava Dec 12, 2013

libnetutils: Expect 1's complement if computed UDP checksum is zero

Per http://tools.ietf.org/html/rfc768:
If the computed  checksum  is zero,  it is transmitted  as all ones (the
equivalent  in one's complement  arithmetic).   An all zero  transmitted
checksum  value means that the transmitter  generated  no checksum  (for
debugging or for higher level protocols that don't care).

Bug: 10642341
Change-Id: Ib6296dcf3f420f87227047a645c99d9f7ea0d437

parent 5f64d528

libnetutils/packet.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -230,6 +230,8 @@ int receive_packet(int s, struct dhcp_msg *msg)
		packet.udp.check = 0;
		sum = finish_sum(checksum(&packet, nread, 0));
		packet.udp.check = temp;
		if (!sum)
		sum = finish_sum(sum);
		if (temp != sum) {
		ALOGW("UDP header checksum failure (0x%x should be 0x%x)", sum, temp);
		return -1;