在参考以下两个链接之后，
https://www.kernel.org/doc/Documentation/networking/packet_mmap.txt
https://sites.google.com/site/packetmmap/
我写了一个带有两个线程的代码，以使用RX / TX环读写数据包。 两者正在并行运行。 令我惊讶的是，我看到TX线程正在写入的数据包在接收线程中显示为RX数据包。
代码如下：
//gcc packet_mmap_read_write.c -lpthread
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#include <sys/ioctl.h>
#include <arpa/inet.h>
#include <pthread.h>
#include <sys/mman.h>
#include <string.h>
#include <stdlib.h>
#include <net/if.h>
#include <net/if.h>
#include <unistd.h>
#include <stdio.h>
#include <netdb.h>
#include <poll.h>
char const * const card_name = "eth0";
void *rx_ring_code( void *unused_param )
{
int i;
const int sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
if( sock < 0 )
{
perror("socket");
exit(1);
}
i = TPACKET_V3;
if( setsockopt( sock, SOL_PACKET, PACKET_VERSION, &i, sizeof(i) ) < 0 )
{
perror("setsockopt");
exit(1);
}
/* i = ( ( getpid() & 0xffff ) | (PACKET_FANOUT_CPU << 16));
if( setsockopt( sock, SOL_PACKET, PACKET_FANOUT, &i, sizeof(i) ) < 0 )
{
perror("setsockopt");
return NULL;
}
*/
struct tpacket_req3 req =
{
.tp_block_size = 1 << 22,
.tp_frame_size = 1 << 11,
.tp_block_nr = 64,
};
struct ifreq ifr;
strcpy( ifr.ifr_name, card_name );
if (ioctl(sock, SIOCGIFFLAGS, &ifr) == -1)
{
perror("unable to get flags");
return NULL;
}
ifr.ifr_flags |= ( IFF_PROMISC | IFF_UP );
if( ioctl( sock, SIOCSIFFLAGS, &ifr ) == -1 )
{
perror("unable to set flags");
return NULL;
}
req.tp_frame_nr = (req.tp_block_size * req.tp_block_nr) / req.tp_frame_size;
if( setsockopt( sock, SOL_PACKET, PACKET_RX_RING, &req, sizeof(struct tpacket_req3) ) < 0 )
{
perror("setsockopt");
exit(1);
}
uint8_t *const map = mmap( NULL, req.tp_block_size * req.tp_block_nr, PROT_READ|PROT_WRITE, MAP_SHARED | MAP_LOCKED, sock, 0 );
if( map == MAP_FAILED )
{
perror("mmap");
exit(1);
}
struct sockaddr_ll ll =
{
.sll_family = PF_PACKET,
.sll_protocol = htons(ETH_P_ALL),
.sll_ifindex = if_nametoindex(ifr.ifr_name)
};
if (bind(sock, (struct sockaddr *) &ll, sizeof(ll)) < 0)
{
perror("bind");
exit(1);
}
struct pollfd pfd =
{
.fd = sock,
.events = POLLIN | POLLERR,
.revents = 0
};
int block_pos = 0;
int pkt_num = 0;
for( block_pos = 0; 1; block_pos = ((block_pos+1) % req.tp_block_nr) )
{
struct block_desc
{
uint32_t version;
uint32_t offset_to_priv;
struct tpacket_hdr_v1 h1;
} *pbd = (struct block_desc *) ( map + (block_pos * req.tp_block_size) );
if( ( pbd->h1.block_status & TP_STATUS_USER ) == 0 )
{
poll(&pfd, 1, -1);
continue;
}
printf( "number of packets captured: %d\n", pbd->h1.num_pkts );
struct tpacket3_hdr *ppd = (struct tpacket3_hdr *) ((uint8_t *) pbd + pbd->h1.offset_to_first_pkt);
for( i = 0; i<pbd->h1.num_pkts; i++ )
{
printf( "packet Number: %d packet size: %d\n", pkt_num++, ppd->tp_snaplen );
/*uint8_t *pkt_ptr = ((uint8_t *) ppd + ppd->tp_mac);
int j;
for( j=0; j<ppd->tp_snaplen; j++ )
{
printf( "%02X ", pkt_ptr[j] );
}
printf( "\n" );
ppd = (struct tpacket3_hdr *) ((uint8_t *) ppd + ppd->tp_next_offset);*/
}
pbd->h1.block_status = TP_STATUS_KERNEL;
}
munmap(map, req.tp_block_size * req.tp_block_nr);
close(sock);
return 0;
}
void * tx_ring_code( void *unused_param )
{
const int c_packet_sz = 200;
int fd_socket, j;
uint32_t i;
fd_socket = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
if( fd_socket == -1 )
{
perror("socket");
return NULL;
}
struct sockaddr_ll my_addr =
{
.sll_family = AF_PACKET,
.sll_protocol = htons(ETH_P_ALL),
.sll_ifindex = (int)if_nametoindex(card_name)
};
/* bind port */
if( bind( fd_socket, (struct sockaddr *)&my_addr, sizeof(struct sockaddr_ll) ) == -1 )
{
perror("bind");
return NULL;
}
/* prepare Tx ring request */
struct tpacket_req s_packet_req =
{
.tp_block_size = 1<<12,
.tp_frame_size = 1<<12,
.tp_block_nr = 10
};
s_packet_req.tp_frame_nr = (s_packet_req.tp_block_size*s_packet_req.tp_block_nr)/s_packet_req.tp_frame_size;
/* send TX ring request */
if( setsockopt( fd_socket, SOL_PACKET, PACKET_TX_RING, (char *)&s_packet_req, sizeof(s_packet_req) ) < 0 )
{
perror( "setsockopt: PACKET_TX_RING" );
return NULL;
}
/* mmap Tx ring buffers memory */
struct tpacket_hdr * const map = mmap(0, s_packet_req.tp_block_size * s_packet_req.tp_block_nr, PROT_WRITE, MAP_SHARED, fd_socket, 0);
if( map == MAP_FAILED )
{
perror("mmap");
return NULL;
}
for( i=0; i<s_packet_req.tp_block_nr; i++ )
{
struct tpacket_hdr * ps_header = ((struct tpacket_hdr *)((void *)map + (s_packet_req.tp_block_size*i)));
#define my_TPACKET_ALIGN(x) (((x)+(uint64_t)(TPACKET_ALIGNMENT-1))&~((uint64_t)(TPACKET_ALIGNMENT-1)))
char * pkt_ptr = ((void*) ps_header) + my_TPACKET_ALIGN(sizeof(struct tpacket_hdr));
for( j=0; j<c_packet_sz; j++ )
{
pkt_ptr[j] = j; /* fill data in buffer */
}
/* update packet length */
ps_header->tp_len = (uint32_t)c_packet_sz;
ps_header->tp_status = TP_STATUS_SEND_REQUEST;
}
int total_pkts = 0, ec_send, total_bytes = 0;
while( total_pkts<s_packet_req.tp_block_nr )
{
ec_send = sendto( fd_socket, NULL, 0, MSG_DONTWAIT, NULL, sizeof(struct sockaddr_ll) );
if(ec_send < 0)
{
perror("send");
}
else
{
total_pkts += ec_send/(c_packet_sz);
total_bytes += ec_send;
printf("%s %d send %d packets (+%d bytes)\n", __func__, __LINE__, total_pkts, total_bytes );
}
}
munmap( map, s_packet_req.tp_block_size * s_packet_req.tp_block_nr );
close(fd_socket);
return NULL;
}
int main()
{
pthread_t rx_thread, tx_thread;
if( pthread_create( &rx_thread, NULL, rx_ring_code, NULL ) )
{
fprintf( stderr, "%s %d\n", __func__, __LINE__ );
return EXIT_FAILURE;
}
if( pthread_create( &tx_thread, NULL, tx_ring_code, NULL ) )
{
fprintf( stderr, "%s %d\n", __func__, __LINE__ );
return EXIT_FAILURE;
}
if( pthread_join( rx_thread, NULL ) )
{
fprintf( stderr, "%s %d\n", __func__, __LINE__ );
return EXIT_FAILURE;
}
if( pthread_join( tx_thread, NULL ) )
{
fprintf( stderr, "%s %d\n", __func__, __LINE__ );
return EXIT_FAILURE;
}
}
如果有一种方法只能捕获传入的数据包，可以有人帮我吗？