4 files changed, 163 insertions, 0 deletions

diff --git a/c/fd-over-sock/.gitignore b/c/fd-over-sock/.gitignore
new file mode 100644
index 0000000..44aa518
--- /dev/null
+++ b/c/fd-over-sock/.gitignore
@@ -0,0 +1,3 @@
+client
+server
+foo.sock
diff --git a/c/fd-over-sock/Makefile b/c/fd-over-sock/Makefile
new file mode 100644
index 0000000..3c353be
--- /dev/null
+++ b/c/fd-over-sock/Makefile
@@ -0,0 +1,10 @@
+include ../base.mk
+
+all: client server
+client: client.c
+	$(CC) $(CFLAGS) -o $@ $<
+server: server.c
+	$(CC) $(CFLAGS) -o $@ $<
+
+clean:
+	rm -f client server
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;
+}
diff --git a/c/fd-over-sock/server.c b/c/fd-over-sock/server.c
new file mode 100644
index 0000000..948e0ec
--- /dev/null
+++ b/c/fd-over-sock/server.c
@@ -0,0 +1,69 @@
+#include <sys/socket.h>
+#include <sys/un.h>
+
+#include <err.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#define die(...) err(EXIT_FAILURE, __VA_ARGS__)
+
+int
+main(void)
+{
+	int sfd;
+	socklen_t saddrlen = sizeof(struct sockaddr_un);
+	struct sockaddr_un saddr = {
+		.sun_family = AF_UNIX,
+		.sun_path = "foo.sock",
+	};
+
+	if ((sfd = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
+		die("socket");
+	if (bind(sfd, (struct sockaddr *)&saddr, saddrlen) == -1)
+		die("bind");
+	if (listen(sfd, 4) == -1)
+		die("listen");
+
+	for (;;) {
+		int cfd = accept(sfd, NULL, NULL);
+		if (cfd == -1)
+			die("accept");
+
+		struct msghdr msg = {0};
+		char m_buffer[sizeof(size_t) * 2];
+		struct iovec io = {
+			.iov_base = m_buffer,
+			.iov_len = sizeof(m_buffer),
+		};
+		msg.msg_iov = &io;
+		msg.msg_iovlen = 1;
+
+		char c_buffer[256];
+		msg.msg_control = c_buffer;
+		msg.msg_controllen = sizeof(c_buffer);
+
+		if (recvmsg(cfd, &msg, 0) == -1)
+			die("recvmsg");
+
+		struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
+		unsigned char *data = CMSG_DATA(cmsg);
+		int fd = *(int *)data;
+
+		size_t flen, mlen;
+		memcpy(&flen, m_buffer, sizeof(size_t));
+		memcpy(&mlen, m_buffer + sizeof(size_t), sizeof(size_t));
+
+		// printf("len: %zu\n", msg.msg_iov->iov_len);
+		write(STDOUT_FILENO, m_buffer + sizeof(size_t) * 2, mlen);
+		putchar('\n');
+
+		char buf[flen];
+		read(fd, buf, flen);
+		write(STDOUT_FILENO, buf, flen);
+		close(cfd);
+	}
+
+	return EXIT_SUCCESS;
+}