1 files changed, 120 insertions, 0 deletions
diff --git a/vsockserverd.c b/vsockserverd.c
new file mode 100644
index 0000000..1abfff9
--- /dev/null
+++ b/vsockserverd.c
@@ -0,0 +1,120 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+// SPDX-FileCopyrightText: 2020-2021 Alyssa Ross <hi@alyssa.is>
+
+#define _GNU_SOURCE
+
+#include <errno.h>
+#include <inttypes.h>
+#include <poll.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdnoreturn.h>
+#include <sys/wait.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#include "env.h"
+#include "log.h"
+#include "vsock.h"
+
+noreturn static void ex_usage(void)
+{
+	if (verbosity)
+		fprintf(stderr, "Usage: %s [ -1 ] [ -q | -Q | -v ] prog...\n",
+			program_invocation_short_name);
+	exit(EX_USAGE);
+}
+
+int main(int argc, char *argv[])
+{
+	bool notify = false;
+	int opt;
+	pid_t child;
+	uint32_t lcid, lport, rcid, rport;
+	struct pollfd poll_fd =
+		{ .fd = STDIN_FILENO, .events = POLLIN, .revents = 0 };
+
+	while ((opt = getopt(argc, argv, "+1qQv")) != -1) {
+		switch (opt) {
+		case '1':
+			notify = true;
+			break;
+		case 'q':
+		case 'Q':
+		case 'v':
+			set_verbosity(opt);
+			break;
+		default:
+			ex_usage();
+		}
+	}
+
+	// Check that there is something for us to exec into.
+	if (optind > argc - 1)
+		ex_usage();
+
+	// Find out the CID and port of the socket.
+	if (vsock_get_cid_and_port(STDIN_FILENO, &lcid, &lport)) {
+		if (errno == ENOTSOCK || errno == EPROTOTYPE)
+			die(EX_USAGE, "stdin is not an AF_VSOCK socket");
+		diee(EX_OSERR, "getsockname");
+	}
+
+	// Notify the user of our port and indicate readiness.
+	if (notify) {
+		printf("%" PRIu32 "\n", lport);
+		fclose(stdout);
+	}
+
+	// Set our CID and port as environment variables so `prog' can
+	// know them.
+	setenvf("VSOCKLOCALCID", 1, "%" PRIu32, lcid);
+	setenvf("VSOCKLOCALPORT", 1, "%" PRIu32, lport);
+
+	ilog("listening as %" PRIu32 " on port %" PRIu32, lcid, lport);
+
+	// Wait for a connection.
+	while (poll(&poll_fd, 1, -1) != -1) {
+		// On Linux, conn will be blocking.  On other
+		// platforms, this may not be the case.  If other
+		// platforms are to be supported, we'd probably want
+		// to set O_NONBLOCK here.
+		int conn = vsock_accept(STDIN_FILENO, &rcid, &rport);
+		if (conn == -1)
+			diee(EX_OSERR, "accept");
+
+		// Set the client's CID and port as environment
+		// variables so `prog' can know them.
+		setenvf("VSOCKREMOTECID", 1, "%" PRIu32, rcid);
+		setenvf("VSOCKREMOTEPORT", 1, "%" PRIu32, rport);
+
+		ilog("connection from %" PRIu32 " port %" PRIu32, rcid, rport);
+
+		switch (child = fork()) {
+		case -1: diee(EX_OSERR, "fork");
+		case 0:
+			// Set up the connection socket on prog's
+			// stdin and stdout.  This has the happy side
+			// effect of closing the listening socket in
+			// the child, since it's also on stdin.
+			if (dup2(conn, STDIN_FILENO) == -1)
+				diee(EX_OSERR, "dup2");
+			if (dup2(conn, STDOUT_FILENO) == -1)
+				diee(EX_OSERR, "dup2");
+			if (conn != STDIN_FILENO && conn != STDOUT_FILENO)
+				close(conn);
+
+			// exec into `prog'.
+			execvp(argv[optind], &argv[optind]);
+			diee(EX_OSERR, "exec");
+		}
+
+		if (waitpid(child, NULL, 0) == -1)
+			diee(EX_OSERR, "waitpid");
+
+		close(conn);
+	}
+	diee(EX_OSERR, "poll");
+}