doc: packet: add minimal TPACKET_V3 example code
Lost in space for a long time, but it finally came back to us from some ancient code tombs. This patch adds a minimal runnable example of Linux' packet mmap(2) from Chetan Loke's TPACKET_V3. Special thanks to David S. Miller, and also Eric Leblond and Victor Julien! Cc: Eric Leblond <eric@regit.org> Cc: Victor Julien <victor@inliniac.net> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann
David S. Miller
parent
e052f7e64d
commit
4eb0614825
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@ -684,6 +684,333 @@ int main(int argc, char **argp)
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return 0;
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}
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-------------------------------------------------------------------------------
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+ AF_PACKET TPACKET_V3 example
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-------------------------------------------------------------------------------
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AF_PACKET's TPACKET_V3 ring buffer can be configured to use non-static frame
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sizes by doing it's own memory management. It is based on blocks where polling
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works on a per block basis instead of per ring as in TPACKET_V2 and predecessor.
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It is said that TPACKET_V3 brings the following benefits:
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*) ~15 - 20% reduction in CPU-usage
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*) ~20% increase in packet capture rate
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*) ~2x increase in packet density
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*) Port aggregation analysis
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*) Non static frame size to capture entire packet payload
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So it seems to be a good candidate to be used with packet fanout.
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Minimal example code by Daniel Borkmann based on Chetan Loke's lolpcap (compile
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it with gcc -Wall -O2 blob.c, and try things like "./a.out eth0", etc.):
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdint.h>
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#include <string.h>
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#include <assert.h>
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#include <net/if.h>
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#include <arpa/inet.h>
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#include <netdb.h>
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#include <poll.h>
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#include <unistd.h>
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#include <signal.h>
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#include <inttypes.h>
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#include <sys/socket.h>
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#include <sys/mman.h>
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#include <linux/if_packet.h>
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#include <linux/if_ether.h>
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#include <linux/ip.h>
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#define BLOCK_SIZE (1 << 22)
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#define FRAME_SIZE 2048
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#define NUM_BLOCKS 64
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#define NUM_FRAMES ((BLOCK_SIZE * NUM_BLOCKS) / FRAME_SIZE)
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#define BLOCK_RETIRE_TOV_IN_MS 64
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#define BLOCK_PRIV_AREA_SZ 13
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#define ALIGN_8(x) (((x) + 8 - 1) & ~(8 - 1))
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#define BLOCK_STATUS(x) ((x)->h1.block_status)
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#define BLOCK_NUM_PKTS(x) ((x)->h1.num_pkts)
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#define BLOCK_O2FP(x) ((x)->h1.offset_to_first_pkt)
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#define BLOCK_LEN(x) ((x)->h1.blk_len)
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#define BLOCK_SNUM(x) ((x)->h1.seq_num)
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#define BLOCK_O2PRIV(x) ((x)->offset_to_priv)
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#define BLOCK_PRIV(x) ((void *) ((uint8_t *) (x) + BLOCK_O2PRIV(x)))
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#define BLOCK_HDR_LEN (ALIGN_8(sizeof(struct block_desc)))
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#define BLOCK_PLUS_PRIV(sz_pri) (BLOCK_HDR_LEN + ALIGN_8((sz_pri)))
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#ifndef likely
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# define likely(x) __builtin_expect(!!(x), 1)
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#endif
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#ifndef unlikely
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# define unlikely(x) __builtin_expect(!!(x), 0)
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#endif
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struct block_desc {
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uint32_t version;
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uint32_t offset_to_priv;
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struct tpacket_hdr_v1 h1;
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};
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struct ring {
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struct iovec *rd;
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uint8_t *map;
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struct tpacket_req3 req;
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};
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static unsigned long packets_total = 0, bytes_total = 0;
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static sig_atomic_t sigint = 0;
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void sighandler(int num)
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{
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sigint = 1;
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}
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static int setup_socket(struct ring *ring, char *netdev)
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{
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int err, i, fd, v = TPACKET_V3;
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struct sockaddr_ll ll;
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fd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
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if (fd < 0) {
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perror("socket");
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exit(1);
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}
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err = setsockopt(fd, SOL_PACKET, PACKET_VERSION, &v, sizeof(v));
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if (err < 0) {
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perror("setsockopt");
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exit(1);
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}
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memset(&ring->req, 0, sizeof(ring->req));
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ring->req.tp_block_size = BLOCK_SIZE;
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ring->req.tp_frame_size = FRAME_SIZE;
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ring->req.tp_block_nr = NUM_BLOCKS;
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ring->req.tp_frame_nr = NUM_FRAMES;
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ring->req.tp_retire_blk_tov = BLOCK_RETIRE_TOV_IN_MS;
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ring->req.tp_sizeof_priv = BLOCK_PRIV_AREA_SZ;
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ring->req.tp_feature_req_word |= TP_FT_REQ_FILL_RXHASH;
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err = setsockopt(fd, SOL_PACKET, PACKET_RX_RING, &ring->req,
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sizeof(ring->req));
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if (err < 0) {
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perror("setsockopt");
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exit(1);
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}
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ring->map = mmap(NULL, ring->req.tp_block_size * ring->req.tp_block_nr,
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PROT_READ | PROT_WRITE, MAP_SHARED | MAP_LOCKED,
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fd, 0);
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if (ring->map == MAP_FAILED) {
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perror("mmap");
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exit(1);
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}
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ring->rd = malloc(ring->req.tp_block_nr * sizeof(*ring->rd));
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assert(ring->rd);
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for (i = 0; i < ring->req.tp_block_nr; ++i) {
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ring->rd[i].iov_base = ring->map + (i * ring->req.tp_block_size);
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ring->rd[i].iov_len = ring->req.tp_block_size;
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}
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memset(&ll, 0, sizeof(ll));
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ll.sll_family = PF_PACKET;
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ll.sll_protocol = htons(ETH_P_ALL);
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ll.sll_ifindex = if_nametoindex(netdev);
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ll.sll_hatype = 0;
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ll.sll_pkttype = 0;
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ll.sll_halen = 0;
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err = bind(fd, (struct sockaddr *) &ll, sizeof(ll));
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if (err < 0) {
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perror("bind");
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exit(1);
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}
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return fd;
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}
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#ifdef __checked
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static uint64_t prev_block_seq_num = 0;
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void assert_block_seq_num(struct block_desc *pbd)
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{
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if (unlikely(prev_block_seq_num + 1 != BLOCK_SNUM(pbd))) {
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printf("prev_block_seq_num:%"PRIu64", expected seq:%"PRIu64" != "
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"actual seq:%"PRIu64"\n", prev_block_seq_num,
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prev_block_seq_num + 1, (uint64_t) BLOCK_SNUM(pbd));
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exit(1);
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}
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prev_block_seq_num = BLOCK_SNUM(pbd);
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}
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static void assert_block_len(struct block_desc *pbd, uint32_t bytes, int block_num)
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{
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if (BLOCK_NUM_PKTS(pbd)) {
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if (unlikely(bytes != BLOCK_LEN(pbd))) {
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printf("block:%u with %upackets, expected len:%u != actual len:%u\n",
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block_num, BLOCK_NUM_PKTS(pbd), bytes, BLOCK_LEN(pbd));
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exit(1);
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}
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} else {
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if (unlikely(BLOCK_LEN(pbd) != BLOCK_PLUS_PRIV(BLOCK_PRIV_AREA_SZ))) {
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printf("block:%u, expected len:%lu != actual len:%u\n",
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block_num, BLOCK_HDR_LEN, BLOCK_LEN(pbd));
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exit(1);
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}
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}
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}
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static void assert_block_header(struct block_desc *pbd, const int block_num)
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{
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uint32_t block_status = BLOCK_STATUS(pbd);
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if (unlikely((block_status & TP_STATUS_USER) == 0)) {
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printf("block:%u, not in TP_STATUS_USER\n", block_num);
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exit(1);
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}
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assert_block_seq_num(pbd);
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}
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#else
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static inline void assert_block_header(struct block_desc *pbd, const int block_num)
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{
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}
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static void assert_block_len(struct block_desc *pbd, uint32_t bytes, int block_num)
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{
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}
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#endif
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static void display(struct tpacket3_hdr *ppd)
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{
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struct ethhdr *eth = (struct ethhdr *) ((uint8_t *) ppd + ppd->tp_mac);
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struct iphdr *ip = (struct iphdr *) ((uint8_t *) eth + ETH_HLEN);
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if (eth->h_proto == htons(ETH_P_IP)) {
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struct sockaddr_in ss, sd;
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char sbuff[NI_MAXHOST], dbuff[NI_MAXHOST];
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memset(&ss, 0, sizeof(ss));
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ss.sin_family = PF_INET;
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ss.sin_addr.s_addr = ip->saddr;
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getnameinfo((struct sockaddr *) &ss, sizeof(ss),
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sbuff, sizeof(sbuff), NULL, 0, NI_NUMERICHOST);
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memset(&sd, 0, sizeof(sd));
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sd.sin_family = PF_INET;
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sd.sin_addr.s_addr = ip->daddr;
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getnameinfo((struct sockaddr *) &sd, sizeof(sd),
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dbuff, sizeof(dbuff), NULL, 0, NI_NUMERICHOST);
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printf("%s -> %s, ", sbuff, dbuff);
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}
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printf("rxhash: 0x%x\n", ppd->hv1.tp_rxhash);
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}
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static void walk_block(struct block_desc *pbd, const int block_num)
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{
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int num_pkts = BLOCK_NUM_PKTS(pbd), i;
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unsigned long bytes = 0;
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unsigned long bytes_with_padding = BLOCK_PLUS_PRIV(BLOCK_PRIV_AREA_SZ);
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struct tpacket3_hdr *ppd;
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assert_block_header(pbd, block_num);
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ppd = (struct tpacket3_hdr *) ((uint8_t *) pbd + BLOCK_O2FP(pbd));
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for (i = 0; i < num_pkts; ++i) {
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bytes += ppd->tp_snaplen;
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if (ppd->tp_next_offset)
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bytes_with_padding += ppd->tp_next_offset;
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else
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bytes_with_padding += ALIGN_8(ppd->tp_snaplen + ppd->tp_mac);
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display(ppd);
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ppd = (struct tpacket3_hdr *) ((uint8_t *) ppd + ppd->tp_next_offset);
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__sync_synchronize();
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}
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assert_block_len(pbd, bytes_with_padding, block_num);
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packets_total += num_pkts;
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bytes_total += bytes;
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}
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void flush_block(struct block_desc *pbd)
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{
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BLOCK_STATUS(pbd) = TP_STATUS_KERNEL;
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__sync_synchronize();
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}
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static void teardown_socket(struct ring *ring, int fd)
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{
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munmap(ring->map, ring->req.tp_block_size * ring->req.tp_block_nr);
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free(ring->rd);
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close(fd);
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}
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int main(int argc, char **argp)
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{
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int fd, err;
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socklen_t len;
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struct ring ring;
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struct pollfd pfd;
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unsigned int block_num = 0;
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struct block_desc *pbd;
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struct tpacket_stats_v3 stats;
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if (argc != 2) {
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fprintf(stderr, "Usage: %s INTERFACE\n", argp[0]);
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return EXIT_FAILURE;
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}
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signal(SIGINT, sighandler);
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memset(&ring, 0, sizeof(ring));
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fd = setup_socket(&ring, argp[argc - 1]);
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assert(fd > 0);
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memset(&pfd, 0, sizeof(pfd));
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pfd.fd = fd;
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pfd.events = POLLIN | POLLERR;
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pfd.revents = 0;
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while (likely(!sigint)) {
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pbd = (struct block_desc *) ring.rd[block_num].iov_base;
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retry_block:
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if ((BLOCK_STATUS(pbd) & TP_STATUS_USER) == 0) {
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poll(&pfd, 1, -1);
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goto retry_block;
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}
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walk_block(pbd, block_num);
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flush_block(pbd);
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block_num = (block_num + 1) % NUM_BLOCKS;
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}
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len = sizeof(stats);
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err = getsockopt(fd, SOL_PACKET, PACKET_STATISTICS, &stats, &len);
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if (err < 0) {
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perror("getsockopt");
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exit(1);
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}
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fflush(stdout);
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printf("\nReceived %u packets, %lu bytes, %u dropped, freeze_q_cnt: %u\n",
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stats.tp_packets, bytes_total, stats.tp_drops,
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stats.tp_freeze_q_cnt);
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teardown_socket(&ring, fd);
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return 0;
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}
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-------------------------------------------------------------------------------
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+ PACKET_TIMESTAMP
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-------------------------------------------------------------------------------
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