diff -urN /tmp/null/if_packet.h mmap-test/if_packet.h
--- /tmp/null/if_packet.h	1970-01-01 01:00:00.000000000 +0100
+++ mmap-test/if_packet.h	2008-07-09 12:56:08.000000000 +0200
@@ -0,0 +1,144 @@
+#ifndef __LINUX_IF_PACKET_H
+#define __LINUX_IF_PACKET_H
+
+#include <linux/types.h>
+
+struct sockaddr_pkt
+{
+	unsigned short spkt_family;
+	unsigned char spkt_device[14];
+	__be16 spkt_protocol;
+};
+
+struct sockaddr_ll
+{
+	unsigned short	sll_family;
+	__be16		sll_protocol;
+	int		sll_ifindex;
+	unsigned short	sll_hatype;
+	unsigned char	sll_pkttype;
+	unsigned char	sll_halen;
+	unsigned char	sll_addr[8];
+};
+
+/* Packet types */
+
+#define PACKET_HOST		0		/* To us		*/
+#define PACKET_BROADCAST	1		/* To all		*/
+#define PACKET_MULTICAST	2		/* To group		*/
+#define PACKET_OTHERHOST	3		/* To someone else 	*/
+#define PACKET_OUTGOING		4		/* Outgoing of any type */
+/* These ones are invisible by user level */
+#define PACKET_LOOPBACK		5		/* MC/BRD frame looped back */
+#define PACKET_FASTROUTE	6		/* Fastrouted frame	*/
+
+/* Packet socket options */
+
+#define PACKET_ADD_MEMBERSHIP		1
+#define PACKET_DROP_MEMBERSHIP		2
+#define PACKET_RECV_OUTPUT		3
+/* Value 4 is still used by obsolete turbo-packet. */
+#define PACKET_RX_RING			5
+#define PACKET_STATISTICS		6
+#define PACKET_COPY_THRESH		7
+#define PACKET_AUXDATA			8
+#define PACKET_ORIGDEV			9
+#define PACKET_VERSION			10
+#define PACKET_HDRLEN			11
+
+struct tpacket_stats
+{
+	unsigned int	tp_packets;
+	unsigned int	tp_drops;
+};
+
+struct tpacket_auxdata
+{
+	__u32		tp_status;
+	__u32		tp_len;
+	__u32		tp_snaplen;
+	__u16		tp_mac;
+	__u16		tp_net;
+	__u16		tp_vlan_tci;
+};
+
+struct tpacket_hdr
+{
+	unsigned long	tp_status;
+#define TP_STATUS_KERNEL	0
+#define TP_STATUS_USER		1
+#define TP_STATUS_COPY		2
+#define TP_STATUS_LOSING	4
+#define TP_STATUS_CSUMNOTREADY	8
+	unsigned int	tp_len;
+	unsigned int	tp_snaplen;
+	unsigned short	tp_mac;
+	unsigned short	tp_net;
+	unsigned int	tp_sec;
+	unsigned int	tp_usec;
+};
+
+#define TPACKET_ALIGNMENT	16
+#define TPACKET_ALIGN(x)	(((x)+TPACKET_ALIGNMENT-1)&~(TPACKET_ALIGNMENT-1))
+#define TPACKET_HDRLEN		(TPACKET_ALIGN(sizeof(struct tpacket_hdr)) + sizeof(struct sockaddr_ll))
+
+struct tpacket2_hdr
+{
+	__u32		tp_status;
+	__u32		tp_len;
+	__u32		tp_snaplen;
+	__u16		tp_mac;
+	__u16		tp_net;
+	__u32		tp_sec;
+	__u32		tp_nsec;
+#ifdef TEST_VLAN_TCI
+	__u16		tp_vlan_tci;
+#endif
+};
+
+#ifdef __KERNEL__
+#define TPACKET2_HDRLEN		(TPACKET_ALIGN(sizeof(struct tpacket2_hdr)) + sizeof(struct sockaddr_ll))
+#else
+#define TPACKET2_HDRLEN(x)	(TPACKET_ALIGN(x) + sizeof(struct sockaddr_ll))
+#endif
+
+enum tpacket_versions
+{
+	TPACKET_V1,
+	TPACKET_V2,
+};
+
+/*
+   Frame structure:
+
+   - Start. Frame must be aligned to TPACKET_ALIGNMENT=16
+   - struct tpacket_hdr
+   - pad to TPACKET_ALIGNMENT=16
+   - struct sockaddr_ll
+   - Gap, chosen so that packet data (Start+tp_net) alignes to TPACKET_ALIGNMENT=16
+   - Start+tp_mac: [ Optional MAC header ]
+   - Start+tp_net: Packet data, aligned to TPACKET_ALIGNMENT=16.
+   - Pad to align to TPACKET_ALIGNMENT=16
+ */
+
+struct tpacket_req
+{
+	unsigned int	tp_block_size;	/* Minimal size of contiguous block */
+	unsigned int	tp_block_nr;	/* Number of blocks */
+	unsigned int	tp_frame_size;	/* Size of frame */
+	unsigned int	tp_frame_nr;	/* Total number of frames */
+};
+
+struct packet_mreq
+{
+	int		mr_ifindex;
+	unsigned short	mr_type;
+	unsigned short	mr_alen;
+	unsigned char	mr_address[8];
+};
+
+#define PACKET_MR_MULTICAST	0
+#define PACKET_MR_PROMISC	1
+#define PACKET_MR_ALLMULTI	2
+
+#endif
diff -urN /tmp/null/Makefile mmap-test/Makefile
--- /tmp/null/Makefile	1970-01-01 01:00:00.000000000 +0100
+++ mmap-test/Makefile	2008-07-09 03:21:21.000000000 +0200
@@ -0,0 +1,3 @@
+CFLAGS	+= -O2 -I. -Wall -g
+
+all: test
diff -urN /tmp/null/test.c mmap-test/test.c
--- /tmp/null/test.c	1970-01-01 01:00:00.000000000 +0100
+++ mmap-test/test.c	2008-07-09 12:56:40.000000000 +0200
@@ -0,0 +1,150 @@
+#include <unistd.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/mman.h>
+#include <poll.h>
+#include <arpa/inet.h>
+#include <linux/types.h>
+#include <linux/socket.h>
+#include <linux/if_ether.h>
+
+#define V2
+#ifdef V2
+#define TEST_VLAN_TCI 1
+#endif
+
+#include "if_packet.h"
+
+int main(int argc, char **argv)
+{
+	struct sockaddr_ll lladdr;
+	struct tpacket_req req;
+#ifdef V2
+	struct tpacket2_hdr *hdr;
+#else
+	struct tpacket_hdr *hdr;
+#endif
+	unsigned int hdrlen;
+	int val;
+	socklen_t len;
+	void *ring;
+	unsigned int head;
+	unsigned int total = 0;
+	int fd;
+
+	fd = socket(AF_PACKET, SOCK_RAW, 0);
+	if (fd < 0) {
+		perror("socket");
+		return 1;
+	}
+
+#ifdef V2
+	val = TPACKET_V2;
+	len = sizeof(val);
+	if (getsockopt(fd, SOL_PACKET, PACKET_HDRLEN, &val, &len) < 0) {
+		perror("setsockopt(PACKET_HDRLEN)");
+		return 1;
+	}
+	hdrlen = val;
+
+	printf("hdrlen=%u sizeof(struct tpacket2_hdr)=%Zu\n",
+		hdrlen, sizeof(struct tpacket2_hdr));
+
+	val = TPACKET_V2;
+	if (setsockopt(fd, SOL_PACKET, PACKET_VERSION, &val, sizeof(val)) < 0) {
+		perror("setsockopt(PACKET_VERSION)");
+		return 1;
+	}
+#else
+	hdrlen = sizeof(struct tpacket_hdr);
+#endif
+
+	memset(&req, 0, sizeof(req));
+	req.tp_block_size	= 16 * 4096;
+	req.tp_block_nr		= 16;
+	req.tp_frame_size	= 1024;
+	req.tp_frame_nr		= 16 * 64;
+
+	if (setsockopt(fd, SOL_PACKET, PACKET_RX_RING, &req, sizeof(req)) < 0) {
+		perror("setsockopt");
+		return 1;
+	}
+
+	ring = mmap(NULL, req.tp_block_nr * req.tp_block_size,
+		    PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if ((long)ring == -1L) {
+		perror("mmap");
+		return 1;
+	}
+
+	memset(&lladdr, 0, sizeof(lladdr));
+	lladdr.sll_family = AF_PACKET;
+	lladdr.sll_protocol = htons(ETH_P_ALL);
+	lladdr.sll_ifindex = 2;
+
+	if (bind(fd, (struct sockaddr *)&lladdr, sizeof(lladdr)) < 0) {
+		perror("bind");
+		return 1;
+	}
+
+	hdr = ring;
+	head = 0;
+
+	while (1) {
+		unsigned int cnt = 0;
+		struct pollfd pfds[1];
+
+		pfds[0].fd	= fd;
+		pfds[0].events	= POLLIN | POLLERR;
+		pfds[0].revents	= 0;
+
+		if (poll(pfds, 1, -1) < 0 && errno != EINTR) {
+			perror("poll");
+			return 1;
+		}
+
+		if (pfds[0].revents & POLLERR) {
+			char buf[16384];
+			recv(fd, buf, sizeof(buf), MSG_DONTWAIT | MSG_ERRQUEUE);
+			printf("error %d\n", errno);
+			continue;
+		}
+
+		if (!(pfds[0].revents & POLLIN))
+			continue;
+
+		while (hdr->tp_status != TP_STATUS_KERNEL) {
+			struct sockaddr_ll *sll;
+			unsigned char *data = (void *)hdr + hdr->tp_mac;
+			unsigned int i;
+
+			printf("%.4u ring[%u]: tp_status=%u tp_len=%u "
+			       "tp_snaplen=%u\n",
+				total, head, hdr->tp_status, hdr->tp_len, hdr->tp_snaplen);
+#ifdef TEST_VLAN_TCI
+			printf("tp_vlan_tci=%u id=%u\n",
+			       hdr->tp_vlan_tci, hdr->tp_vlan_tci & 0xfff);
+#endif
+			for (i = 0; i < (hdr->tp_snaplen > 32 ? 32 : hdr->tp_snaplen); i++)
+				printf("%.2x ", data[i]);
+			printf("\n");
+
+			sll = (void *)hdr + TPACKET_ALIGN(hdrlen);
+			printf("sll_family=%u sll_protocol=%u sll_ifindex=%d sll_hatype=%u "
+			       "sll_pkttype=%u sll_halen=%u\n",
+			       sll->sll_family, ntohs(sll->sll_protocol),
+			       sll->sll_ifindex, sll->sll_hatype,
+			       sll->sll_pkttype, sll->sll_halen);
+			hdr->tp_status = TP_STATUS_KERNEL;
+
+			head = head == req.tp_frame_nr - 1 ? 0 : head + 1;
+			hdr = ring + head * req.tp_frame_size;
+			cnt++, total++;
+		}
+		printf("received %u consecutive entries, %u total\n\n", cnt, total);
+	}
+	return 0;
+}