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#include <vector>
#include <string>
#include <tuple>
#include <utility>
#include <cstdio>
#include <cstring>
#include <cassert>
#include <unistd.h>
#include <signal.h>
#include <sys/select.h>
#include <sys/wait.h>
#include "handler.h"
using namespace std;
struct Pipes {
int rfd, wfd;
};
static pair<pid_t, Pipes> start_process(const vector<string> &cmd) {
int host2child[2], child2host[2];
if (pipe(host2child) < 0 || pipe(child2host) < 0) {
perror("pipe");
exit(1);
}
pid_t pid = fork();
if (pid == 0) {
close(host2child[1]);
close(child2host[0]);
dup2(host2child[0], STDIN_FILENO);
dup2(child2host[1], STDOUT_FILENO);
vector<char*> argv(cmd.size() + 1);
for (size_t i = 0; i < cmd.size(); i++) {
argv[i] = (char*)cmd[i].data();
fprintf(stderr, "argv[%zu] = %p (%s)\n", i, cmd[i].data(), cmd[i].data());
}
argv[cmd.size()] = nullptr;
execvp(argv[0], argv.data());
perror("execvp");
exit(1);
}
if (pid < 0) {
perror("fork");
exit(1);
}
close(host2child[0]);
close(child2host[1]);
return make_pair(pid, Pipes{child2host[0], host2child[1]});
}
static bool poll_process_exited(pid_t pid) {
int status;
pid_t ret = waitpid(pid, &status, WNOHANG);
if (ret == 0) return false;
if (ret < 0) {
if (errno == EINTR) return false; // wut? we said WNOHANG, right?
perror("wait");
return true;
}
assert(ret == pid);
return WIFEXITED(status);
}
static void wait_process_exited(pid_t pid) {
while (true) {
int status;
pid_t ret = waitpid(pid, &status, 0);
if (ret < 0) {
if (errno == EINTR) continue;
perror("wait");
exit(1);
}
if (ret == 0) continue; // wut?
assert(ret == pid);
if (WIFEXITED(pid)) break;
}
}
int main(int argc, char **argv) {
vector<string> server_args(argc - 1);
for (int i = 0; i < argc - 1; i++) server_args[i] = argv[i + 1];
// make sure we actually receive the signal
signal(SIGCHLD, [](int) {});
pid_t child_pid;
Pipes pipes;
tie(child_pid, pipes) = start_process(server_args);
int exit_code = 0;
while (true) {
fd_set inset;
FD_ZERO(&inset);
FD_SET(pipes.rfd, &inset);
int ret = select(pipes.rfd + 1, &inset, nullptr, nullptr, nullptr);
if (poll_process_exited(child_pid)) {
child_pid = -1;
goto exit_cleanup;
}
if (ret < 0) {
if (errno == EINTR) continue;
perror("select");
exit_code = 1;
goto exit_cleanup;
}
if (FD_ISSET(pipes.rfd, &inset)) {
uint8_t buffer[24];
size_t cursor = 0;
while (cursor < 24) {
ssize_t nread = read(pipes.rfd, buffer + cursor, 24 - cursor);
if (nread < 0) {
perror("read");
goto exit_cleanup;
}
cursor += nread;
}
if (memcmp(buffer, "payl", 4) != 0) {
fprintf(stderr, "Invalid event message from server: id bytes '%c%c%c%c'\n",
buffer[0], buffer[1], buffer[2], buffer[3]);
fprintf(stderr, "<");
fwrite(buffer, 1, 24, stderr);
fprintf(stderr, ">\n");
exit_code = 1;
goto exit_cleanup;
}
uint32_t source_addr = *(uint32_t*)&buffer[4];
array<uint8_t, 16> payload;
memcpy(payload.data(), &buffer[8], 16);
uint16_t seqnum = handle_icmp(source_addr, payload);
if (write(pipes.wfd, &seqnum, 2) != 2) {
perror("write");
exit_code = 1;
goto exit_cleanup;
}
}
}
exit_cleanup:
if (child_pid != -1) {
kill(child_pid, SIGTERM);
wait_process_exited(child_pid);
}
return exit_code;
}
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