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diff -up dhcp-4.2.5/common/packet.c.ffff dhcp-4.2.5/common/packet.c
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--- dhcp-4.2.5/common/packet.c.ffff	2013-10-07 17:21:18.000000000 +0200
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+++ dhcp-4.2.5/common/packet.c	2013-10-07 17:47:34.689600497 +0200
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@@ -326,6 +326,7 @@ decode_udp_ip_header(struct interface_in
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   len = ulen - sizeof(udp);
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   usum = udp.uh_sum;
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+  if (usum == 0xffff) usum = 0;
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   udp.uh_sum = 0;
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   /* XXX: We have to pass &udp, because we have to zero the checksum