在使用 PACKET_MMAP (PACKET_RX_RING) 捕获以太网数据包时,在 100KB/s 或更高的数据速率下,我有超过 50% 的数据包丢失。这种技术普遍吗?
将 PACKET_MMAP 与 PACKET_RX_RING 一起使用时,代码/参数/逻辑是否有任何改进的机会或空间以减少数据包丢失
#include <stdio.h>
#include <stdio.h>
#include <sys/socket.h>
#include <net/if.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <sys/mman.h>
#include <poll.h>
#include <signal.h>
void handle_frame(struct tpacket_hdr* tphdr, struct sockaddr_ll* addr, char* l2content, char * l3content){
if(tphdr->tp_status & TP_STATUS_USER){
fwrite(l2content,tphdr->tp_snaplen,1,pcapfile);
tphdr->tp_status = TP_STATUS_KERNEL;
}
}
int main(){
file1 = fopen("file1.cap","a+");
int fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
if (fd == -1) {
perror("socket");
exit(1);
}
struct tpacket_req req = {0};
req.tp_frame_size = TPACKET_ALIGN(TPACKET_HDRLEN + ETH_HLEN) + TPACKET_ALIGN(1500);
req.tp_block_size = sysconf(_SC_PAGESIZE);
while (req.tp_block_size < req.tp_frame_size) {
req.tp_block_size <<= 1;
}
req.tp_block_nr = 4;
size_t frames_per_buffer = req.tp_block_size / req.tp_frame_size;
req.tp_frame_nr = req.tp_block_nr * frames_per_buffer;
int version = TPACKET_V1;
(setsockopt(fd, SOL_PACKET, PACKET_VERSION, &version, sizeof(version));
setsockopt(fd, SOL_PACKET, PACKET_RX_RING, (void*)&req, sizeof(req));
size_t rx_ring_size = req.tp_block_nr * req.tp_block_size;
char* rx_ring = mmap(0, rx_ring_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
struct pollfd fds[1] = {0};
fds[0].fd = fd;
fds[0].events = POLLIN;
size_t frame_idx = 0;
char* frame_ptr = rx_ring;
while (1) {
struct tpacket_hdr* tphdr = (struct tpacket_hdr*)frame_ptr;
while (!(tphdr->tp_status & TP_STATUS_USER)) {
if (poll(fds, 1, -1) == -1) {
perror("poll");
exit(1);
}
}
struct sockaddr_ll* addr = (struct sockaddr_ll*)(frame_ptr + TPACKET_HDRLEN - sizeof(struct sockaddr_ll));
char* l2content = frame_ptr + tphdr->tp_mac;
char* l3content = frame_ptr + tphdr->tp_net;
handle_frame(tphdr, addr, l2content, l3content);
frame_idx = (frame_idx + 1) % req.tp_frame_nr;
int buffer_idx = frame_idx / frames_per_buffer;
char* buffer_ptr = rx_ring + buffer_idx * req.tp_block_size;
int frame_idx_diff = frame_idx % frames_per_buffer;
frame_ptr = buffer_ptr + frame_idx_diff * req.tp_frame_size;
}
fflush(pcapfile);
fclose(pcapfile);
}