diff options
author | Daniel Borkmann <dborkman@redhat.com> | 2013-06-06 14:08:13 (GMT) |
---|---|---|
committer | David S. Miller <davem@davemloft.net> | 2013-06-07 21:39:05 (GMT) |
commit | d70a3f887a38cb0acc7233a1d05f15c2b6e0be2b (patch) | |
tree | 942562a2ce0e048ae72c8c202835fee2c418b11b /Documentation | |
parent | 93a306aef5eef70e524500884ccca52c5dd19e17 (diff) | |
download | linux-d70a3f887a38cb0acc7233a1d05f15c2b6e0be2b.tar.xz |
doc: packet: simplify tpacket example code
This patch simplifies the tpacket_v3 example code a bit by getting rid
of unecessary macro wrappers, removing some debugging code so that it is
more to the point, and also adds a header comment. Now this example code
is the very minimum one needs to start from when dealing with tpacket_v3
and ~100 lines smaller than before.
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/networking/packet_mmap.txt | 133 |
1 files changed, 28 insertions, 105 deletions
diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt index 23dd80e..8572796 100644 --- a/Documentation/networking/packet_mmap.txt +++ b/Documentation/networking/packet_mmap.txt @@ -704,6 +704,12 @@ So it seems to be a good candidate to be used with packet fanout. Minimal example code by Daniel Borkmann based on Chetan Loke's lolpcap (compile it with gcc -Wall -O2 blob.c, and try things like "./a.out eth0", etc.): +/* Written from scratch, but kernel-to-user space API usage + * dissected from lolpcap: + * Copyright 2011, Chetan Loke <loke.chetan@gmail.com> + * License: GPL, version 2.0 + */ + #include <stdio.h> #include <stdlib.h> #include <stdint.h> @@ -722,27 +728,6 @@ it with gcc -Wall -O2 blob.c, and try things like "./a.out eth0", etc.): #include <linux/if_ether.h> #include <linux/ip.h> -#define BLOCK_SIZE (1 << 22) -#define FRAME_SIZE 2048 - -#define NUM_BLOCKS 64 -#define NUM_FRAMES ((BLOCK_SIZE * NUM_BLOCKS) / FRAME_SIZE) - -#define BLOCK_RETIRE_TOV_IN_MS 64 -#define BLOCK_PRIV_AREA_SZ 13 - -#define ALIGN_8(x) (((x) + 8 - 1) & ~(8 - 1)) - -#define BLOCK_STATUS(x) ((x)->h1.block_status) -#define BLOCK_NUM_PKTS(x) ((x)->h1.num_pkts) -#define BLOCK_O2FP(x) ((x)->h1.offset_to_first_pkt) -#define BLOCK_LEN(x) ((x)->h1.blk_len) -#define BLOCK_SNUM(x) ((x)->h1.seq_num) -#define BLOCK_O2PRIV(x) ((x)->offset_to_priv) -#define BLOCK_PRIV(x) ((void *) ((uint8_t *) (x) + BLOCK_O2PRIV(x))) -#define BLOCK_HDR_LEN (ALIGN_8(sizeof(struct block_desc))) -#define BLOCK_PLUS_PRIV(sz_pri) (BLOCK_HDR_LEN + ALIGN_8((sz_pri))) - #ifndef likely # define likely(x) __builtin_expect(!!(x), 1) #endif @@ -765,7 +750,7 @@ struct ring { static unsigned long packets_total = 0, bytes_total = 0; static sig_atomic_t sigint = 0; -void sighandler(int num) +static void sighandler(int num) { sigint = 1; } @@ -774,6 +759,8 @@ static int setup_socket(struct ring *ring, char *netdev) { int err, i, fd, v = TPACKET_V3; struct sockaddr_ll ll; + unsigned int blocksiz = 1 << 22, framesiz = 1 << 11; + unsigned int blocknum = 64; fd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); if (fd < 0) { @@ -788,13 +775,12 @@ static int setup_socket(struct ring *ring, char *netdev) } memset(&ring->req, 0, sizeof(ring->req)); - ring->req.tp_block_size = BLOCK_SIZE; - ring->req.tp_frame_size = FRAME_SIZE; - ring->req.tp_block_nr = NUM_BLOCKS; - ring->req.tp_frame_nr = NUM_FRAMES; - ring->req.tp_retire_blk_tov = BLOCK_RETIRE_TOV_IN_MS; - ring->req.tp_sizeof_priv = BLOCK_PRIV_AREA_SZ; - ring->req.tp_feature_req_word |= TP_FT_REQ_FILL_RXHASH; + ring->req.tp_block_size = blocksiz; + ring->req.tp_frame_size = framesiz; + ring->req.tp_block_nr = blocknum; + ring->req.tp_frame_nr = (blocksiz * blocknum) / framesiz; + ring->req.tp_retire_blk_tov = 60; + ring->req.tp_feature_req_word = TP_FT_REQ_FILL_RXHASH; err = setsockopt(fd, SOL_PACKET, PACKET_RX_RING, &ring->req, sizeof(ring->req)); @@ -804,8 +790,7 @@ static int setup_socket(struct ring *ring, char *netdev) } ring->map = mmap(NULL, ring->req.tp_block_size * ring->req.tp_block_nr, - PROT_READ | PROT_WRITE, MAP_SHARED | MAP_LOCKED, - fd, 0); + PROT_READ | PROT_WRITE, MAP_SHARED | MAP_LOCKED, fd, 0); if (ring->map == MAP_FAILED) { perror("mmap"); exit(1); @@ -835,58 +820,6 @@ static int setup_socket(struct ring *ring, char *netdev) return fd; } -#ifdef __checked -static uint64_t prev_block_seq_num = 0; - -void assert_block_seq_num(struct block_desc *pbd) -{ - if (unlikely(prev_block_seq_num + 1 != BLOCK_SNUM(pbd))) { - printf("prev_block_seq_num:%"PRIu64", expected seq:%"PRIu64" != " - "actual seq:%"PRIu64"\n", prev_block_seq_num, - prev_block_seq_num + 1, (uint64_t) BLOCK_SNUM(pbd)); - exit(1); - } - - prev_block_seq_num = BLOCK_SNUM(pbd); -} - -static void assert_block_len(struct block_desc *pbd, uint32_t bytes, int block_num) -{ - if (BLOCK_NUM_PKTS(pbd)) { - if (unlikely(bytes != BLOCK_LEN(pbd))) { - printf("block:%u with %upackets, expected len:%u != actual len:%u\n", - block_num, BLOCK_NUM_PKTS(pbd), bytes, BLOCK_LEN(pbd)); - exit(1); - } - } else { - if (unlikely(BLOCK_LEN(pbd) != BLOCK_PLUS_PRIV(BLOCK_PRIV_AREA_SZ))) { - printf("block:%u, expected len:%lu != actual len:%u\n", - block_num, BLOCK_HDR_LEN, BLOCK_LEN(pbd)); - exit(1); - } - } -} - -static void assert_block_header(struct block_desc *pbd, const int block_num) -{ - uint32_t block_status = BLOCK_STATUS(pbd); - - if (unlikely((block_status & TP_STATUS_USER) == 0)) { - printf("block:%u, not in TP_STATUS_USER\n", block_num); - exit(1); - } - - assert_block_seq_num(pbd); -} -#else -static inline void assert_block_header(struct block_desc *pbd, const int block_num) -{ -} -static void assert_block_len(struct block_desc *pbd, uint32_t bytes, int block_num) -{ -} -#endif - static void display(struct tpacket3_hdr *ppd) { struct ethhdr *eth = (struct ethhdr *) ((uint8_t *) ppd + ppd->tp_mac); @@ -916,37 +849,27 @@ static void display(struct tpacket3_hdr *ppd) static void walk_block(struct block_desc *pbd, const int block_num) { - int num_pkts = BLOCK_NUM_PKTS(pbd), i; + int num_pkts = pbd->h1.num_pkts, i; unsigned long bytes = 0; - unsigned long bytes_with_padding = BLOCK_PLUS_PRIV(BLOCK_PRIV_AREA_SZ); struct tpacket3_hdr *ppd; - assert_block_header(pbd, block_num); - - ppd = (struct tpacket3_hdr *) ((uint8_t *) pbd + BLOCK_O2FP(pbd)); + ppd = (struct tpacket3_hdr *) ((uint8_t *) pbd + + pbd->h1.offset_to_first_pkt); for (i = 0; i < num_pkts; ++i) { bytes += ppd->tp_snaplen; - if (ppd->tp_next_offset) - bytes_with_padding += ppd->tp_next_offset; - else - bytes_with_padding += ALIGN_8(ppd->tp_snaplen + ppd->tp_mac); - display(ppd); - ppd = (struct tpacket3_hdr *) ((uint8_t *) ppd + ppd->tp_next_offset); - __sync_synchronize(); + ppd = (struct tpacket3_hdr *) ((uint8_t *) ppd + + ppd->tp_next_offset); } - assert_block_len(pbd, bytes_with_padding, block_num); - packets_total += num_pkts; bytes_total += bytes; } -void flush_block(struct block_desc *pbd) +static void flush_block(struct block_desc *pbd) { - BLOCK_STATUS(pbd) = TP_STATUS_KERNEL; - __sync_synchronize(); + pbd->h1.block_status = TP_STATUS_KERNEL; } static void teardown_socket(struct ring *ring, int fd) @@ -962,7 +885,7 @@ int main(int argc, char **argp) socklen_t len; struct ring ring; struct pollfd pfd; - unsigned int block_num = 0; + unsigned int block_num = 0, blocks = 64; struct block_desc *pbd; struct tpacket_stats_v3 stats; @@ -984,15 +907,15 @@ int main(int argc, char **argp) while (likely(!sigint)) { pbd = (struct block_desc *) ring.rd[block_num].iov_base; -retry_block: - if ((BLOCK_STATUS(pbd) & TP_STATUS_USER) == 0) { + + if ((pbd->h1.block_status & TP_STATUS_USER) == 0) { poll(&pfd, 1, -1); - goto retry_block; + continue; } walk_block(pbd, block_num); flush_block(pbd); - block_num = (block_num + 1) % NUM_BLOCKS; + block_num = (block_num + 1) % blocks; } len = sizeof(stats); |