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udptimeoutchecker.c
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udptimeoutchecker.c
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#include <sys/mman.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <netdb.h>
#include <stdlib.h>
#include <signal.h>
#include <time.h>
static void serve1(int socket_fd) {
char buf[128];
memset(buf, 0, sizeof(buf));
struct sockaddr_storage sa;
socklen_t sa_len = sizeof(sa);
ssize_t ret = recvfrom(socket_fd, buf, sizeof(buf)-1, 0, (struct sockaddr*)&sa, &sa_len);
if (ret == -1) {
return;
}
unsigned long int secs1;
unsigned long int nanos1;
unsigned long int secs2;
unsigned long int nanos2;
if(sscanf(buf, "%lu%lu%lu%lu", &secs1, &nanos1, &secs2, &nanos2) != 4) {
return;
}
if (secs1+secs2 > 600 || nanos1 >= 1000*1000*1000 || nanos2 >= 1000*1000*1000) {
return;
}
if (fork() != 0) {
// SIGCHLD is ignored, so there should be no zombies
return;
}
// child process:
struct timespec ts1, ts2;
ts1.tv_sec = secs1;
ts1.tv_nsec = nanos1;
ts2.tv_sec = secs2;
ts2.tv_nsec = nanos2;
if (-1 == clock_nanosleep(CLOCK_MONOTONIC, 0, &ts1, NULL)) _exit(1);
sendto(socket_fd, "B\n", 2, 0, (struct sockaddr*)&sa, sa_len);
if (-1 == clock_nanosleep(CLOCK_MONOTONIC, 0, &ts2, NULL)) _exit(2);
sendto(socket_fd, "A\n", 2, 0, (struct sockaddr*)&sa, sa_len);
_exit(0);
}
int try(int s, int seconds) {
fprintf(stderr, "Trying with timeout %d seconds...", seconds);
struct timeval tv;
tv.tv_sec = seconds + 2;
tv.tv_usec = 0;
setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));
char buf[128];
int l;
l = snprintf(buf, sizeof(buf), "0 0 %d 0\n", seconds);
l = send(s, buf, l, 0);
if (l == -1) {
perror("send");
return -1;
}
l = recv(s, buf, sizeof(buf), 0);
if(l<1) {
fprintf(stderr, "Fail B...\n");
return -1;
}
if(buf[0] != 'B') {
fprintf(stderr, "Strange B\n");
return -1;
}
l = recv(s, buf, sizeof(buf), 0);
if(l<1) {
fprintf(stderr, "FAIL\n");
return -1;
}
if(buf[0] != 'A') {
fprintf(stderr, "Strange A\n");
return -1;
}
fprintf(stderr, "OK\n");
return 0;
}
int one_experiment(int s) {
int max_to = 1;
int num_fails = 0;
// Phase 1 - double the timeout until it fails
for(;;) {
if (try(s, max_to) == 0) {
num_fails = 0;
if (max_to >= 512) {
return max_to;
}
max_to *= 2;
} else {
num_fails += 1;
if (num_fails == 3) {
break;
}
}
}
if (max_to == 1) return 0;
int min_to = max_to / 2;
for(;;) {
if (max_to - min_to <= 2) {
fprintf(stderr, "Intermediate result: %d\n", min_to);
return min_to;
}
int candidate = (min_to + max_to) / 2;
if (try(s, candidate) == 0) {
min_to = candidate;
} else {
max_to = candidate;
}
}
}
static int numcmp(const void *p1, const void *p2) {
return (*(const int*)p1) - (*(const int*)p2);
}
int probe(int s) {
int exps[3];
int i;
for(i=0; i<sizeof(exps)/sizeof(exps[0]); ++i) {
exps[i] = one_experiment(s);
}
qsort(exps, sizeof(exps)/sizeof(exps[0]), sizeof(exps[0]), &numcmp);
printf("%d\n", exps[1]);
return 0;
}
int main(int argc, char* argv[]) {
if (argc != 4 && argc != 6) {
fprintf(stderr, "Usage:\n");
fprintf(stderr, " udptimeoutchecker serve listen_addr listen_port \n");
fprintf(stderr, " udptimeoutchecker probe bind_addr bind_port connect_addr connect_port\n");
fprintf(stderr, "Probes time for which UDP connection though a NAT stays open.\n");
fprintf(stderr, "Example:\n");
fprintf(stderr, " udptimeoutchecker serve 0.0.0.0 1909\n");
fprintf(stderr, " udptimeoutchecker probe 0.0.0.0 0 vi-server.org 1909\n");
fprintf(stderr, "\n");
return 1;
}
const char* cmd = argv[1];
const char* bind_addr_ = argv[2];
const char* bind_port_ = argv[3];
const char* send_addr_ = argv[4];
const char* send_port_ = argv[5];
if (!!strcmp(cmd, "serve") && !!strcmp(cmd, "probe")) {
fprintf(stderr, "Command should be 'serve' or 'probe'\n");
return 1;
}
if (!strcmp(cmd,"probe") && argc != 6) {
fprintf(stderr, "Not enough arguments for probe command\n");
return 1;
}
{
struct sigaction siga;
memset(&siga, 0, sizeof(siga));
siga.sa_handler = SIG_IGN;
sigaction(SIGCHLD, &siga, NULL);
}
struct addrinfo hints;
struct addrinfo *recv_addr;
struct addrinfo *send_addr;
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_socktype = SOCK_DGRAM; /* Datagram socket */
hints.ai_family = AF_INET;
hints.ai_flags = AI_PASSIVE;
int gai_error;
gai_error=getaddrinfo(bind_addr_,bind_port_, &hints, &recv_addr);
if (gai_error) { fprintf(stderr, "getaddrinfo 1: %s\n",gai_strerror(gai_error)); return 4; }
if (!recv_addr) { fprintf(stderr, "getaddrinfo returned no addresses\n"); return 6; }
if (recv_addr->ai_next) {
fprintf(stderr, "Warning: using only one of addresses retuned by getaddrinfo\n");
}
if (!strcmp(cmd,"probe")) {
hints.ai_flags &= !AI_PASSIVE;
gai_error=getaddrinfo(send_addr_, send_port_, &hints, &send_addr);
if (gai_error) { fprintf(stderr, "getaddrinfo 2: %s\n",gai_strerror(gai_error)); return 13; }
if (!send_addr) { fprintf(stderr, "getaddrinfo 2 returned no addresses\n"); return 15; }
if (send_addr->ai_next) {
fprintf(stderr, "Warning: using only one of addresses retuned by getaddrinfo 2\n");
}
}
int s;
s = socket(recv_addr->ai_family, recv_addr->ai_socktype, recv_addr->ai_protocol);
if (s == -1) { perror("socket"); return 7; }
{
int one = 1;
setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &one, sizeof one);
}
if (bind(s, recv_addr->ai_addr, recv_addr->ai_addrlen)) { perror("bind"); return 5; }
if (!strcmp(cmd,"serve")) {
for(;;) {
serve1(s);
usleep(250*1000);
}
}
if (!strcmp(cmd,"probe")) {
if (-1 == connect(s, send_addr->ai_addr, send_addr->ai_addrlen)) {
perror("connect");
return 6;
}
return probe(s);
}
}