nbdc.c

#include <stdint.h>
#include <sys/ioctl.h>
#include <linux/nbd.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <fcntl.h>
#include <unistd.h>

void worker(int fd) {
	struct nbd_request rq;
	struct nbd_reply rp;
	uint32_t l;
	int rc;
	struct iovec iv[2];

	char *buf = calloc(1, 1048576);
	for (;;) {
		rc = read(fd, &rq, sizeof(rq));
		if (rc != sizeof(rq)) {
			continue;
		}

		l = ntohl(rq.len);
		if (l == 0) {
			continue;
		}

		// rq.type 0 

		memcpy(rp.handle, rq.handle, 8);
		rp.magic = htonl(0x67446698);
		rp.error = htonl(0);
		iv[0].iov_base = &rp;
		iv[0].iov_len = sizeof(rp);
		iv[1].iov_base = buf;
		iv[1].iov_len = l;
		rc = writev(fd, iv, 2);
	}
}

int main(int argc, char *argv[]) {
	int fd;

	fd = open(argv[1], O_RDWR);
	int sv[2];
	sv[0] = socket(AF_UNIX, SOCK_STREAM, 0);
	sv[1] = socket(AF_UNIX, SOCK_STREAM, 0);

	struct sockaddr_un addr;
	memset(&addr, 0, sizeof(addr));
	addr.sun_family = AF_UNIX;
	addr.sun_path[0] = '\0';
	addr.sun_path[1] = '9';
	bind(sv[1], (struct sockaddr*)&addr, sizeof(addr));
	listen(sv[1], 5);

	int rc = fork();
	switch (rc) {
	case 0: {
		int u = accept(sv[1], NULL, NULL);
		worker(u);
		return 0;
	}
	}

	connect(sv[0], (struct sockaddr*)&addr, sizeof(addr));
	sleep(5);
	ioctl(fd, NBD_SET_SOCK, sv[0]);
	ioctl(fd, NBD_SET_BLKSIZE, (unsigned long) 512);
	ioctl(fd, NBD_SET_SIZE_BLOCKS, (unsigned long long) 10000200400ull);
	ioctl(fd, NBD_SET_TIMEOUT, (unsigned long) 60);
	ioctl(fd, NBD_SET_FLAGS, NBD_FLAG_READ_ONLY);
	ioctl(fd, NBD_DO_IT);
}