ruby – 每秒测量出站请求数？

$sudo tcpdump -c 10 -i eth0 "tcp[tcpflags] & (tcp-syn) != 0 and dst 192.168.0.1"
tcpdump: verbose output suppressed,use -v or -vv for full protocol decode
listening on eth0,link-type EN10MB (Ethernet),capture size 65535 bytes
18:26:24.800308 IP haig.59419 > 192.168.0.1.telnet: Flags [S],seq 3197302320,win 14600,options [mss 1460,sackOK,TS val 19460844 ecr 0,nop,wscale 7],length 0
...
18:26:27.420132 IP haig.59428 > 192.168.0.1.telnet: Flags [S],seq 1238498237,TS val 19461106 ecr 0,length 0
10 packets captured
10 packets received by filter
0 packets dropped by kernel

您可以使用/usr/bin/time或内置shell的时间,或者对输出中的时间戳进行一些算术运算,以获得每秒的平均速率. (使用十个以上的数据包 – 这只是为了演示.)

更新

我写了一个小程序来运行tcpdump(8),计算数据包,并报告在指定的时间间隔内发送了多少数据包：

# ./counter --host 192.168.0.1 --interface eth0 --interval 3
2 requests in 3 seconds; average 0.67 req/seq
20 requests in 3 seconds; average 6.67 req/seq
19 requests in 3 seconds; average 6.33 req/seq
19 requests in 3 seconds; average 6.33 req/seq
^C
# ./counter --host 192.168.0.1 --interface eth0 --interval 5
30 requests in 5 seconds; average 6.00 req/seq
20 requests in 5 seconds; average 4.00 req/seq
1176 requests in 5 seconds; average 235.20 req/seq
1414 requests in 5 seconds; average 282.80 req/seq
0 requests in 5 seconds; average 0.00 req/seq
^C

因为它要求tcpdump(8)使用行缓冲输出,我有点害怕它可能无法超过每秒200-300个请求,至少在我的硬件上.但是没有行缓冲输出,tcpdump(8)会等到它的输出缓冲区(详见setvbuf(3))在发送任何输出之前都已满,导致极其抖动的结果.

但如果您的连接速度不是那么高,那么这可能会满足您的需求.如果您的连接速率较高,那么这个小小的黑客可能最好被忽略 – 这让我觉得可能iptables(8)可以计算流.

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <getopt.h>
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/types.h>

#define CMDLEN 1024
#define TCPDUMPLEN 4096

int show_stats;
long counter;

void alarm_handler(int signum)
{
    show_stats = 1;
}

void install_handler(void)
{
    struct sigaction sa;

    memset(&sa,sizeof(sa));

    sigemptyset(&sa.sa_mask);
    sa.sa_handler = &alarm_handler;
    if (sigaction(SIGALRM,&sa,NULL) == -1) {
        perror("Can't install alarm handler");
        exit(1);
    }
}

int count_lines(char *p,int bytes)
{
    int counter = 0;
    char *i;
    for (i=p; i < p+bytes ; i++) {
        if (*i == 'n')
            counter++;
    }
    return counter;
}

int spawn_tcpdump(char *host,char *interface)
{
    int fd[2];
    pid_t child;

    if (pipe(fd) == -1) {
        perror("Can't create pipes");
        exit(1);
    }

    child = fork();

    if (child == -1) {
        perror("Can't fork(2) for tcpdump");
        exit(1);
    }

    if (child == 0) {
        int null;
        int len;
        char syn_and_dst[CMDLEN];

        len = snprintf(syn_and_dst,CMDLEN,"tcp[tcpflags] & (tcp-syn) != 0 and dst %s",host);

        if (len > CMDLEN) {
            perror("host argument too long");
            exit(1);
        }

        /* child writes into pipe */
        close(fd[0]);
        dup2(fd[1],STDOUT_FILENO);

        /* throw away first two lines of tcpdump output */
        null = open("/dev/null",O_WRONLY);

        if (null == -1) {
            perror("Can't open /dev/null");
            exit(1);
        }

        dup2(null,STDERR_FILENO);

        execl("/usr/sbin/tcpdump","tcpdump","-l","-n","-s 96","-i",interface,syn_and_dst,(char *) NULL);
        /* can't reach */
        perror("Cannot execute tcpdump");
        exit(1); 
    } else {
        /* parent reads from pipe */
        close(fd[1]);
        return fd[0];
    }
}

int main(int argc,char *argv[])
{
    int tcpdump;
    char *host;
    char *interface;
    long interval;


    while (1) {
        int option_index;
        int c;

        static struct option opts[] = {
            {"host",required_argument,NULL,'h'},{"interface",'i'},{"interval",'n'},{0,0},};

        c = getopt_long(argc,argv,"",opts,&option_index);

        if (c == -1)
            break;

        switch (c) {
            case 'h':
                host = strdup(optarg);
                break;
            case 'i':
                interface = strdup(optarg);
                break;
            case 'n': {
                    char *endptr;
                    interval = strtol(optarg,&endptr,10);
                    if (!(optarg[0] != '' && endptr[0] == '')) {
                        fprintf(stderr,"Expected integer; invalid"
                                " input '%s'n",optarg);
                        exit(1);
                    }
                }
                break;
            default:
                fprintf(stderr,"Option parsing errorn");
                exit(1);
        }

    }

    if (optind < argc) {
        fprintf(stderr,"unexpected arguments: ");
        while (optind < argc) {
            fprintf(stderr,"%s ",argv[optind++]);
        }
        fprintf(stderr,"n");
    }

    tcpdump = spawn_tcpdump(host,interface);

    install_handler();
    alarm(interval);

    while(1) {
        if (show_stats) {
            printf("%ld requests in %ld seconds; average %2.2f req/seqn",counter,interval,(double)counter / (double)interval);
            counter = 0;
            show_stats = 0;
            alarm(interval);
        } else {
            char buffer[TCPDUMPLEN];
            int ret;

            memset(buffer,TCPDUMPLEN);
            ret = read(tcpdump,buffer,TCPDUMPLEN);
            if (ret == -1 && errno == EINTR) {
                /* nop */
            } else if (ret == -1) {
                perror("read");
                exit(1);
            } else {
                counter += count_lines(buffer,ret);
            }
        }
    }

    exit(0);
}