From 2fb71458d07f4ddc6f04773ae75341300fda8905 Mon Sep 17 00:00:00 2001
From: Thomas Voss <mail@thomasvoss.com>
Date: Mon, 11 Dec 2023 17:24:34 +0100
Subject: Add fc-over-sock

---
 c/fd-over-sock/client.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 c/fd-over-sock/client.c

(limited to 'c/fd-over-sock/client.c')

diff --git a/c/fd-over-sock/client.c b/c/fd-over-sock/client.c
new file mode 100644
index 0000000..506c2ca
--- /dev/null
+++ b/c/fd-over-sock/client.c
@@ -0,0 +1,81 @@
+#define _GNU_SOURCE
+#include <sys/mman.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/un.h>
+
+#include <err.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define die(...) err(EXIT_FAILURE, __VA_ARGS__)
+
+typedef uint8_t u8;
+
+int
+main(int argc, char **argv)
+{
+	int fd, sfd;
+	void *shm;
+	socklen_t saddrlen = sizeof(struct sockaddr_un);
+	struct stat sb;
+	struct sockaddr_un saddr = {
+		.sun_family = AF_UNIX,
+		.sun_path = "foo.sock",
+	};
+
+	*argv = basename(*argv);
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s file\n", *argv);
+		exit(EXIT_FAILURE);
+	}
+
+	if ((fd = open(argv[1], O_RDONLY)) == -1)
+		die("open: %s", argv[1]);
+	if (fstat(fd, &sb) == -1)
+		die("fstat: %s", argv[1]);
+	shm = mmap(NULL, sb.st_size, PROT_READ, MAP_SHARED, fd, 0);
+	if (shm == MAP_FAILED)
+		die("mmap: %s", argv[1]);
+
+	if ((sfd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
+		die("socket");
+	if (connect(sfd, &saddr, saddrlen) == -1)
+		die("connect");
+
+	u8 msg[sizeof(size_t) * 2 + sizeof("hello world") - 1];
+	char buf[CMSG_SPACE(sizeof(int))];
+	struct iovec iov = {
+		.iov_base = msg,
+		.iov_len = sizeof(msg) - 1,
+	};
+	struct msghdr hdr = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = buf,
+		.msg_controllen = CMSG_SPACE(sizeof(int)),
+	};
+	struct cmsghdr *cmsg = CMSG_FIRSTHDR(&hdr);
+	cmsg->cmsg_level = SOL_SOCKET;
+	cmsg->cmsg_type = SCM_RIGHTS;
+	cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+	*(int *)CMSG_DATA(cmsg) = fd;
+
+	size_t len = sb.st_size;
+	size_t len2 = 11;
+	memcpy(msg, &len, sizeof(size_t));
+	memcpy(msg + sizeof(size_t), &len2, sizeof(size_t));
+	memcpy(msg + sizeof(size_t) * 2, "hello, world", 11);
+
+	if (sendmsg(sfd, &hdr, 0) == -1)
+		die("sendmsg");
+
+	munmap(shm, sb.st_size);
+	close(fd);
+	close(sfd);
+	return EXIT_SUCCESS;
+}
-- 
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