diff -up dhcp-4.2.0/common/bpf.c.xen dhcp-4.2.0/common/bpf.c
--- dhcp-4.2.0/common/bpf.c.xen	2009-11-19 20:48:59.000000000 -0500
+++ dhcp-4.2.0/common/bpf.c	2010-09-23 05:24:01.000000000 -0400
@@ -485,7 +485,7 @@ ssize_t receive_packet (interface, buf, 
 		offset = decode_udp_ip_header (interface,
 					       interface -> rbuf,
 					       interface -> rbuf_offset,
-  					       from, hdr.bh_caplen, &paylen);
+  					       from, hdr.bh_caplen, &paylen, 0);
 
 		/* If the IP or UDP checksum was bad, skip the packet... */
 		if (offset < 0) {
diff -up dhcp-4.2.0/common/dlpi.c.xen dhcp-4.2.0/common/dlpi.c
--- dhcp-4.2.0/common/dlpi.c.xen	2009-11-19 20:49:00.000000000 -0500
+++ dhcp-4.2.0/common/dlpi.c	2010-09-23 05:24:05.000000000 -0400
@@ -694,7 +694,7 @@ ssize_t receive_packet (interface, buf, 
 	length -= offset;
 #endif
 	offset = decode_udp_ip_header (interface, dbuf, bufix,
-				       from, length, &paylen);
+				       from, length, &paylen, 0);
 
 	/*
 	 * If the IP or UDP checksum was bad, skip the packet...
diff -up dhcp-4.2.0/common/lpf.c.xen dhcp-4.2.0/common/lpf.c
--- dhcp-4.2.0/common/lpf.c.xen	2009-07-23 14:52:19.000000000 -0400
+++ dhcp-4.2.0/common/lpf.c	2010-09-23 05:24:09.000000000 -0400
@@ -29,18 +29,33 @@
 #include "dhcpd.h"
 #if defined (USE_LPF_SEND) || defined (USE_LPF_RECEIVE)
 #include <sys/ioctl.h>
+#include <sys/socket.h>
 #include <sys/uio.h>
 #include <errno.h>
 
 #include <asm/types.h>
 #include <linux/filter.h>
 #include <linux/if_ether.h>
+#include <linux/if_packet.h>
 #include <netinet/in_systm.h>
 #include "includes/netinet/ip.h"
 #include "includes/netinet/udp.h"
 #include "includes/netinet/if_ether.h"
 #include <net/if.h>
 
+#ifndef PACKET_AUXDATA
+#define PACKET_AUXDATA 8
+
+struct tpacket_auxdata
+{
+	__u32		tp_status;
+	__u32		tp_len;
+	__u32		tp_snaplen;
+	__u16		tp_mac;
+	__u16		tp_net;
+};
+#endif
+
 /* Reinitializes the specified interface after an address change.   This
    is not required for packet-filter APIs. */
 
@@ -66,10 +81,14 @@ int if_register_lpf (info)
 	struct interface_info *info;
 {
 	int sock;
-	struct sockaddr sa;
+	union {
+		struct sockaddr_ll ll;
+		struct sockaddr common;
+	} sa;
+	struct ifreq ifr;
 
 	/* Make an LPF socket. */
-	if ((sock = socket(PF_PACKET, SOCK_PACKET,
+	if ((sock = socket(PF_PACKET, SOCK_RAW,
 			   htons((short)ETH_P_ALL))) < 0) {
 		if (errno == ENOPROTOOPT || errno == EPROTONOSUPPORT ||
 		    errno == ESOCKTNOSUPPORT || errno == EPFNOSUPPORT ||
@@ -84,11 +103,16 @@ int if_register_lpf (info)
 		log_fatal ("Open a socket for LPF: %m");
 	}
 
+	memset (&ifr, 0, sizeof ifr);
+	strncpy (ifr.ifr_name, (const char *)info -> ifp, sizeof ifr.ifr_name);
+	if (ioctl (sock, SIOCGIFINDEX, &ifr))
+		log_fatal ("Failed to get interface index: %m");
+
 	/* Bind to the interface name */
 	memset (&sa, 0, sizeof sa);
-	sa.sa_family = AF_PACKET;
-	strncpy (sa.sa_data, (const char *)info -> ifp, sizeof sa.sa_data);
-	if (bind (sock, &sa, sizeof sa)) {
+	sa.ll.sll_family = AF_PACKET;
+	sa.ll.sll_ifindex = ifr.ifr_ifindex;
+	if (bind (sock, &sa.common, sizeof sa)) {
 		if (errno == ENOPROTOOPT || errno == EPROTONOSUPPORT ||
 		    errno == ESOCKTNOSUPPORT || errno == EPFNOSUPPORT ||
 		    errno == EAFNOSUPPORT || errno == EINVAL) {
@@ -170,9 +194,18 @@ static void lpf_gen_filter_setup (struct
 void if_register_receive (info)
 	struct interface_info *info;
 {
+	int val;
+
 	/* Open a LPF device and hang it on this interface... */
 	info -> rfdesc = if_register_lpf (info);
 
+	val = 1;
+	if (setsockopt (info -> rfdesc, SOL_PACKET, PACKET_AUXDATA, &val,
+			sizeof val) < 0) {
+		if (errno != ENOPROTOOPT)
+			log_fatal ("Failed to set auxiliary packet data: %m");
+	}
+
 #if defined (HAVE_TR_SUPPORT)
 	if (info -> hw_address.hbuf [0] == HTYPE_IEEE802)
 		lpf_tr_filter_setup (info);
@@ -294,7 +327,6 @@ ssize_t send_packet (interface, packet, 
 	double hh [16];
 	double ih [1536 / sizeof (double)];
 	unsigned char *buf = (unsigned char *)ih;
-	struct sockaddr sa;
 	int result;
 	int fudge;
 
@@ -315,15 +347,7 @@ ssize_t send_packet (interface, packet, 
 				(unsigned char *)raw, len);
 	memcpy (buf + ibufp, raw, len);
 
-	/* For some reason, SOCK_PACKET sockets can't be connected,
-	   so we have to do a sentdo every time. */
-	memset (&sa, 0, sizeof sa);
-	sa.sa_family = AF_PACKET;
-	strncpy (sa.sa_data,
-		 (const char *)interface -> ifp, sizeof sa.sa_data);
-
-	result = sendto (interface -> wfdesc,
-			 buf + fudge, ibufp + len - fudge, 0, &sa, sizeof sa);
+	result = write (interface -> wfdesc, buf + fudge, ibufp + len - fudge);
 	if (result < 0)
 		log_error ("send_packet: %m");
 	return result;
@@ -340,14 +364,35 @@ ssize_t receive_packet (interface, buf, 
 {
 	int length = 0;
 	int offset = 0;
+	int nocsum = 0;
 	unsigned char ibuf [1536];
 	unsigned bufix = 0;
 	unsigned paylen;
+	unsigned char cmsgbuf[CMSG_LEN(sizeof(struct tpacket_auxdata))];
+	struct iovec iov = {
+		.iov_base = ibuf,
+		.iov_len = sizeof ibuf,
+	};
+	struct msghdr msg = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = cmsgbuf,
+		.msg_controllen = sizeof(cmsgbuf),
+	};
+	struct cmsghdr *cmsg;
 
-	length = read (interface -> rfdesc, ibuf, sizeof ibuf);
+	length = recvmsg (interface -> rfdesc, &msg, 0);
 	if (length <= 0)
 		return length;
 
+	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+		if (cmsg->cmsg_level == SOL_PACKET &&
+		    cmsg->cmsg_type == PACKET_AUXDATA) {
+			struct tpacket_auxdata *aux = (void *)CMSG_DATA(cmsg);
+			nocsum = aux->tp_status & TP_STATUS_CSUMNOTREADY;
+		}
+	}
+
 	bufix = 0;
 	/* Decode the physical header... */
 	offset = decode_hw_header (interface, ibuf, bufix, hfrom);
@@ -364,7 +409,7 @@ ssize_t receive_packet (interface, buf, 
 
 	/* Decode the IP and UDP headers... */
 	offset = decode_udp_ip_header (interface, ibuf, bufix, from,
-				       (unsigned)length, &paylen);
+				       (unsigned)length, &paylen, nocsum);
 
 	/* If the IP or UDP checksum was bad, skip the packet... */
 	if (offset < 0)
diff -up dhcp-4.2.0/common/nit.c.xen dhcp-4.2.0/common/nit.c
--- dhcp-4.2.0/common/nit.c.xen	2009-11-19 20:49:01.000000000 -0500
+++ dhcp-4.2.0/common/nit.c	2010-09-23 05:24:18.000000000 -0400
@@ -369,7 +369,7 @@ ssize_t receive_packet (interface, buf, 
 
 	/* Decode the IP and UDP headers... */
 	offset = decode_udp_ip_header (interface, ibuf, bufix,
-				       from, length, &paylen);
+				       from, length, &paylen, 0);
 
 	/* If the IP or UDP checksum was bad, skip the packet... */
 	if (offset < 0)
diff -up dhcp-4.2.0/common/packet.c.xen dhcp-4.2.0/common/packet.c
--- dhcp-4.2.0/common/packet.c.xen	2009-07-23 14:52:20.000000000 -0400
+++ dhcp-4.2.0/common/packet.c	2010-09-23 05:24:21.000000000 -0400
@@ -211,7 +211,7 @@ ssize_t
 decode_udp_ip_header(struct interface_info *interface,
 		     unsigned char *buf, unsigned bufix,
 		     struct sockaddr_in *from, unsigned buflen,
-		     unsigned *rbuflen)
+		     unsigned *rbuflen, int nocsum)
 {
   unsigned char *data;
   struct ip ip;
@@ -322,7 +322,7 @@ decode_udp_ip_header(struct interface_in
 					   8, IPPROTO_UDP + ulen))));
 
   udp_packets_seen++;
-  if (usum && usum != sum) {
+  if (!nocsum && usum && usum != sum) {
 	  udp_packets_bad_checksum++;
 	  if (udp_packets_seen > 4 &&
 	      (udp_packets_seen / udp_packets_bad_checksum) < 2) {
diff -up dhcp-4.2.0/common/upf.c.xen dhcp-4.2.0/common/upf.c
--- dhcp-4.2.0/common/upf.c.xen	2009-11-19 20:49:01.000000000 -0500
+++ dhcp-4.2.0/common/upf.c	2010-09-23 05:24:25.000000000 -0400
@@ -320,7 +320,7 @@ ssize_t receive_packet (interface, buf, 
 
 	/* Decode the IP and UDP headers... */
 	offset = decode_udp_ip_header (interface, ibuf, bufix,
-				       from, length, &paylen);
+				       from, length, &paylen, 0);
 
 	/* If the IP or UDP checksum was bad, skip the packet... */
 	if (offset < 0)
diff -up dhcp-4.2.0/includes/dhcpd.h.xen dhcp-4.2.0/includes/dhcpd.h
--- dhcp-4.2.0/includes/dhcpd.h.xen	2010-06-01 13:29:59.000000000 -0400
+++ dhcp-4.2.0/includes/dhcpd.h	2010-09-23 05:24:32.000000000 -0400
@@ -2769,7 +2769,7 @@ ssize_t decode_hw_header PROTO ((struct 
 				 unsigned, struct hardware *));
 ssize_t decode_udp_ip_header PROTO ((struct interface_info *, unsigned char *,
 				     unsigned, struct sockaddr_in *,
-				     unsigned, unsigned *));
+				     unsigned, unsigned *, int));
 
 /* ethernet.c */
 void assemble_ethernet_header PROTO ((struct interface_info *, unsigned char *,
