1 files changed, 159 insertions, 0 deletions
diff --git a/url_handler/main.cpp b/url_handler/main.cpp
new file mode 100644
index 0000000..47166db
--- /dev/null
+++ b/url_handler/main.cpp
@@ -0,0 +1,159 @@
+#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;
+}