diff options
Diffstat (limited to 'Documentation/networking/packet_mmap.txt')
| -rw-r--r-- | Documentation/networking/packet_mmap.txt | 368 |
1 files changed, 362 insertions, 6 deletions
diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt index 94444b152fb..23dd80e82b8 100644 --- a/Documentation/networking/packet_mmap.txt +++ b/Documentation/networking/packet_mmap.txt @@ -685,14 +685,342 @@ int main(int argc, char **argp) } ------------------------------------------------------------------------------- ++ AF_PACKET TPACKET_V3 example +------------------------------------------------------------------------------- + +AF_PACKET's TPACKET_V3 ring buffer can be configured to use non-static frame +sizes by doing it's own memory management. It is based on blocks where polling +works on a per block basis instead of per ring as in TPACKET_V2 and predecessor. + +It is said that TPACKET_V3 brings the following benefits: + *) ~15 - 20% reduction in CPU-usage + *) ~20% increase in packet capture rate + *) ~2x increase in packet density + *) Port aggregation analysis + *) Non static frame size to capture entire packet payload + +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.): + +#include <stdio.h> +#include <stdlib.h> +#include <stdint.h> +#include <string.h> +#include <assert.h> +#include <net/if.h> +#include <arpa/inet.h> +#include <netdb.h> +#include <poll.h> +#include <unistd.h> +#include <signal.h> +#include <inttypes.h> +#include <sys/socket.h> +#include <sys/mman.h> +#include <linux/if_packet.h> +#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 +#ifndef unlikely +# define unlikely(x) __builtin_expect(!!(x), 0) +#endif + +struct block_desc { + uint32_t version; + uint32_t offset_to_priv; + struct tpacket_hdr_v1 h1; +}; + +struct ring { + struct iovec *rd; + uint8_t *map; + struct tpacket_req3 req; +}; + +static unsigned long packets_total = 0, bytes_total = 0; +static sig_atomic_t sigint = 0; + +void sighandler(int num) +{ + sigint = 1; +} + +static int setup_socket(struct ring *ring, char *netdev) +{ + int err, i, fd, v = TPACKET_V3; + struct sockaddr_ll ll; + + fd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL)); + if (fd < 0) { + perror("socket"); + exit(1); + } + + err = setsockopt(fd, SOL_PACKET, PACKET_VERSION, &v, sizeof(v)); + if (err < 0) { + perror("setsockopt"); + exit(1); + } + + 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; + + err = setsockopt(fd, SOL_PACKET, PACKET_RX_RING, &ring->req, + sizeof(ring->req)); + if (err < 0) { + perror("setsockopt"); + exit(1); + } + + ring->map = mmap(NULL, ring->req.tp_block_size * ring->req.tp_block_nr, + PROT_READ | PROT_WRITE, MAP_SHARED | MAP_LOCKED, + fd, 0); + if (ring->map == MAP_FAILED) { + perror("mmap"); + exit(1); + } + + ring->rd = malloc(ring->req.tp_block_nr * sizeof(*ring->rd)); + assert(ring->rd); + for (i = 0; i < ring->req.tp_block_nr; ++i) { + ring->rd[i].iov_base = ring->map + (i * ring->req.tp_block_size); + ring->rd[i].iov_len = ring->req.tp_block_size; + } + + memset(&ll, 0, sizeof(ll)); + ll.sll_family = PF_PACKET; + ll.sll_protocol = htons(ETH_P_ALL); + ll.sll_ifindex = if_nametoindex(netdev); + ll.sll_hatype = 0; + ll.sll_pkttype = 0; + ll.sll_halen = 0; + + err = bind(fd, (struct sockaddr *) &ll, sizeof(ll)); + if (err < 0) { + perror("bind"); + exit(1); + } + + 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); + struct iphdr *ip = (struct iphdr *) ((uint8_t *) eth + ETH_HLEN); + + if (eth->h_proto == htons(ETH_P_IP)) { + struct sockaddr_in ss, sd; + char sbuff[NI_MAXHOST], dbuff[NI_MAXHOST]; + + memset(&ss, 0, sizeof(ss)); + ss.sin_family = PF_INET; + ss.sin_addr.s_addr = ip->saddr; + getnameinfo((struct sockaddr *) &ss, sizeof(ss), + sbuff, sizeof(sbuff), NULL, 0, NI_NUMERICHOST); + + memset(&sd, 0, sizeof(sd)); + sd.sin_family = PF_INET; + sd.sin_addr.s_addr = ip->daddr; + getnameinfo((struct sockaddr *) &sd, sizeof(sd), + dbuff, sizeof(dbuff), NULL, 0, NI_NUMERICHOST); + + printf("%s -> %s, ", sbuff, dbuff); + } + + printf("rxhash: 0x%x\n", ppd->hv1.tp_rxhash); +} + +static void walk_block(struct block_desc *pbd, const int block_num) +{ + int num_pkts = BLOCK_NUM_PKTS(pbd), 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)); + 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(); + } + + assert_block_len(pbd, bytes_with_padding, block_num); + + packets_total += num_pkts; + bytes_total += bytes; +} + +void flush_block(struct block_desc *pbd) +{ + BLOCK_STATUS(pbd) = TP_STATUS_KERNEL; + __sync_synchronize(); +} + +static void teardown_socket(struct ring *ring, int fd) +{ + munmap(ring->map, ring->req.tp_block_size * ring->req.tp_block_nr); + free(ring->rd); + close(fd); +} + +int main(int argc, char **argp) +{ + int fd, err; + socklen_t len; + struct ring ring; + struct pollfd pfd; + unsigned int block_num = 0; + struct block_desc *pbd; + struct tpacket_stats_v3 stats; + + if (argc != 2) { + fprintf(stderr, "Usage: %s INTERFACE\n", argp[0]); + return EXIT_FAILURE; + } + + signal(SIGINT, sighandler); + + memset(&ring, 0, sizeof(ring)); + fd = setup_socket(&ring, argp[argc - 1]); + assert(fd > 0); + + memset(&pfd, 0, sizeof(pfd)); + pfd.fd = fd; + pfd.events = POLLIN | POLLERR; + pfd.revents = 0; + + while (likely(!sigint)) { + pbd = (struct block_desc *) ring.rd[block_num].iov_base; +retry_block: + if ((BLOCK_STATUS(pbd) & TP_STATUS_USER) == 0) { + poll(&pfd, 1, -1); + goto retry_block; + } + + walk_block(pbd, block_num); + flush_block(pbd); + block_num = (block_num + 1) % NUM_BLOCKS; + } + + len = sizeof(stats); + err = getsockopt(fd, SOL_PACKET, PACKET_STATISTICS, &stats, &len); + if (err < 0) { + perror("getsockopt"); + exit(1); + } + + fflush(stdout); + printf("\nReceived %u packets, %lu bytes, %u dropped, freeze_q_cnt: %u\n", + stats.tp_packets, bytes_total, stats.tp_drops, + stats.tp_freeze_q_cnt); + + teardown_socket(&ring, fd); + return 0; +} + +------------------------------------------------------------------------------- + PACKET_TIMESTAMP ------------------------------------------------------------------------------- The PACKET_TIMESTAMP setting determines the source of the timestamp in -the packet meta information. If your NIC is capable of timestamping -packets in hardware, you can request those hardware timestamps to used. -Note: you may need to enable the generation of hardware timestamps with -SIOCSHWTSTAMP. +the packet meta information for mmap(2)ed RX_RING and TX_RINGs. If your +NIC is capable of timestamping packets in hardware, you can request those +hardware timestamps to be used. Note: you may need to enable the generation +of hardware timestamps with SIOCSHWTSTAMP (see related information from +Documentation/networking/timestamping.txt). PACKET_TIMESTAMP accepts the same integer bit field as SO_TIMESTAMPING. However, only the SOF_TIMESTAMPING_SYS_HARDWARE @@ -704,8 +1032,36 @@ SOF_TIMESTAMPING_RAW_HARDWARE if both bits are set. req |= SOF_TIMESTAMPING_SYS_HARDWARE; setsockopt(fd, SOL_PACKET, PACKET_TIMESTAMP, (void *) &req, sizeof(req)) -If PACKET_TIMESTAMP is not set, a software timestamp generated inside -the networking stack is used (the behavior before this setting was added). +For the mmap(2)ed ring buffers, such timestamps are stored in the +tpacket{,2,3}_hdr structure's tp_sec and tp_{n,u}sec members. To determine +what kind of timestamp has been reported, the tp_status field is binary |'ed +with the following possible bits ... + + TP_STATUS_TS_SYS_HARDWARE + TP_STATUS_TS_RAW_HARDWARE + TP_STATUS_TS_SOFTWARE + +... that are equivalent to its SOF_TIMESTAMPING_* counterparts. For the +RX_RING, if none of those 3 are set (i.e. PACKET_TIMESTAMP is not set), +then this means that a software fallback was invoked *within* PF_PACKET's +processing code (less precise). + +Getting timestamps for the TX_RING works as follows: i) fill the ring frames, +ii) call sendto() e.g. in blocking mode, iii) wait for status of relevant +frames to be updated resp. the frame handed over to the application, iv) walk +through the frames to pick up the individual hw/sw timestamps. + +Only (!) if transmit timestamping is enabled, then these bits are combined +with binary | with TP_STATUS_AVAILABLE, so you must check for that in your +application (e.g. !(tp_status & (TP_STATUS_SEND_REQUEST | TP_STATUS_SENDING)) +in a first step to see if the frame belongs to the application, and then +one can extract the type of timestamp in a second step from tp_status)! + +If you don't care about them, thus having it disabled, checking for +TP_STATUS_AVAILABLE resp. TP_STATUS_WRONG_FORMAT is sufficient. If in the +TX_RING part only TP_STATUS_AVAILABLE is set, then the tp_sec and tp_{n,u}sec +members do not contain a valid value. For TX_RINGs, by default no timestamp +is generated! See include/linux/net_tstamp.h and Documentation/networking/timestamping for more information on hardware timestamps. |