examples/kdigest: add AF_ALG hash example

When built with CONFIG_CRYPTO_USER_API_HASH enabled, Linux exposes a
socket based API for hashing data. When coupled with uring
IOSQE_IO_LINK, file hashing can be done in quite an efficient manner,
as demonstrated in this link-cp.c based example.

Signed-off-by: David Disseldorp <[email protected]>

.gitignore

@@ -14,6 +14,7 @@
 /examples/io_uring-test
 /examples/link-cp
 /examples/ucontext-cp
+/examples/kdigest
 
 /test/232c93d07b74-test
 /test/35fa71a030ca-test

examples/Makefile

@@ -10,7 +10,7 @@ ifneq ($(MAKECMDGOALS),clean)
 include ../config-host.mak
 endif
 
-all_targets += io_uring-test io_uring-cp link-cp
+all_targets += io_uring-test io_uring-cp link-cp kdigest
 
 ifdef CONFIG_HAVE_UCONTEXT
 all_targets += ucontext-cp

examples/kdigest.c

@@ -0,0 +1,292 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * link-cp based proof-of-concept for doing file digests with linked SQEs using
+ * the kernel's AF_ALG API. Needs a bit of error handling and short read love.
+ */
+#include <stdio.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <assert.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/ioctl.h>
+#include <linux/if_alg.h>
+#include "liburing.h"
+
+#define QD	64
+#define BS	(32*1024)
+
+struct io_data {
+	size_t offset;
+	int index;
+	struct iovec iov;
+};
+
+static int infd, outfd;
+static unsigned inflight;
+
+static int setup_context(unsigned entries, struct io_uring *ring)
+{
+	int ret;
+
+	ret = io_uring_queue_init(entries, ring, 0);
+	if (ret < 0) {
+		fprintf(stderr, "queue_init: %s\n", strerror(-ret));
+		return -1;
+	}
+
+	return 0;
+}
+
+static int get_file_size(int fd, off_t *size)
+{
+	struct stat st;
+
+	if (fstat(fd, &st) < 0)
+		return -1;
+	if (S_ISREG(st.st_mode)) {
+		*size = st.st_size;
+		return 0;
+	} else if (S_ISBLK(st.st_mode)) {
+		unsigned long long bytes;
+
+		if (ioctl(fd, BLKGETSIZE64, &bytes) != 0)
+			return -1;
+
+		*size = bytes;
+		return 0;
+	}
+
+	return -1;
+}
+
+static void queue_rw_pair(struct io_uring *ring, off_t size, off_t offset)
+{
+	struct io_uring_sqe *sqe;
+	struct io_data *data;
+	void *ptr;
+
+	ptr = malloc(size + sizeof(*data));
+	assert(ptr);
+	data = ptr + size;
+	data->index = 0;
+	data->offset = offset;
+	data->iov.iov_base = ptr;
+	data->iov.iov_len = size;
+
+	sqe = io_uring_get_sqe(ring);
+	io_uring_prep_readv(sqe, infd, &data->iov, 1, offset);
+	sqe->flags |= IOSQE_IO_LINK;
+	io_uring_sqe_set_data(sqe, data);
+
+	sqe = io_uring_get_sqe(ring);
+	/*
+	 * data must be sent to the hasher in file order. IOSQE_IO_DRAIN is
+	 * needed here to avoid concurrent / out of order send I/Os.
+	 */
+	sqe->flags |= IOSQE_IO_DRAIN;
+	io_uring_prep_send(sqe, outfd, ptr, size, MSG_MORE);
+	io_uring_sqe_set_data(sqe, data);
+}
+
+static int handle_cqe(struct io_uring *ring, struct io_uring_cqe *cqe)
+{
+	struct io_data *data = io_uring_cqe_get_data(cqe);
+	int ret = 0;
+
+	data->index++;
+
+	if (cqe->res < 0) {
+		if (cqe->res == -ECANCELED) {
+			queue_rw_pair(ring, BS, data->offset);
+			inflight += 2;
+		} else {
+			fprintf(stderr, "cqe error: %s\n",
+				strerror(-cqe->res));
+			ret = 1;
+		}
+	}
+
+	if (data->index == 2) {
+		void *ptr = (void *) data - data->iov.iov_len;
+
+		free(ptr);
+	}
+	io_uring_cqe_seen(ring, cqe);
+	return ret;
+}
+
+static int digest_file(struct io_uring *ring, off_t insize)
+{
+	struct io_uring_cqe *cqe;
+	size_t this_size;
+	off_t offset;
+
+	offset = 0;
+	while (insize) {
+		int has_inflight = inflight;
+		int depth;
+
+		while (insize && inflight < QD) {
+			this_size = BS;
+			if (this_size > insize)
+				this_size = insize;
+			queue_rw_pair(ring, this_size, offset);
+			offset += this_size;
+			insize -= this_size;
+			inflight += 2;
+		}
+
+		if (has_inflight != inflight) {
+			if (io_uring_submit(ring) < 0)
+				return 1;
+		}
+
+		if (insize)
+			depth = QD;
+		else
+			depth = 1;
+		while (inflight >= depth) {
+			int ret;
+
+			ret = io_uring_wait_cqe(ring, &cqe);
+			if (ret < 0) {
+				fprintf(stderr, "wait cqe: %s\n",
+					strerror(-ret));
+				return 1;
+			}
+			if (handle_cqe(ring, cqe))
+				return 1;
+			inflight--;
+		}
+	}
+
+	return 0;
+}
+
+static int get_result(struct io_uring *ring, const char *alg, const char *file)
+{
+	struct io_uring_sqe *sqe;
+	struct io_uring_cqe *cqe;
+	int i, ret;
+	/* buffer must be large enough to carry longest hash result */
+	uint8_t buf[4096];
+
+	sqe = io_uring_get_sqe(ring);
+	memset(buf, 0, sizeof(buf));
+	io_uring_prep_read(sqe, outfd, buf, sizeof(buf), 0);
+	if (io_uring_submit(ring) < 0)
+		return 1;
+
+	ret = io_uring_wait_cqe(ring, &cqe);
+	if (ret < 0) {
+		fprintf(stderr, "wait cqe: %s\n", strerror(-ret));
+		return 1;
+	}
+
+	if (cqe->res < 0 || cqe->res > sizeof(buf)) {
+		fprintf(stderr, "cqe error: %s\n", strerror(-cqe->res));
+		ret = 1;
+	} else {
+		fprintf(stdout, "uring %s(%s) returned(len=%u): ",
+			alg, file, cqe->res);
+		for (i = 0; i < cqe->res; i++)
+			fprintf(stdout, "%02x", buf[i]);
+		putc('\n', stdout);
+		ret = 0;
+	}
+
+	io_uring_cqe_seen(ring, cqe);
+	return ret;
+}
+
+int main(int argc, char *argv[])
+{
+	struct io_uring ring;
+	const char *alg = argv[1];
+	const char *infile = argv[2];
+	size_t alg_len;
+	struct sockaddr_alg sa = {
+		.salg_family = AF_ALG,
+		.salg_type = "hash",
+	};
+	int sfd = -1;
+	off_t insize;
+	int ret;
+
+	if (argc < 3) {
+		fprintf(stderr, "%s: algorithm infile\n", argv[0]);
+		return 1;
+	}
+
+	alg_len = strlen(alg);
+	if (alg_len >= sizeof(sa.salg_name)) {
+		fprintf(stderr, "algorithm name too long\n");
+		return 1;
+	}
+	/* +1 for null terminator */
+	memcpy(sa.salg_name, alg, alg_len + 1);
+
+	infd = open(infile, O_RDONLY);
+	if (infd < 0) {
+		perror("open infile");
+		return 1;
+	}
+
+	sfd = socket(AF_ALG, SOCK_SEQPACKET, 0);
+	if (sfd < 0) {
+		if (errno == EAFNOSUPPORT)
+			fprintf(stderr, "kernel AF_ALG support not available. "
+				"CONFIG_CRYPTO_USER_API_HASH required.\n");
+		else
+			perror("AF_ALG socket");
+		return 1;
+	}
+
+	if (bind(sfd, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
+		if (errno == ENOENT)
+			fprintf(stderr, "AF_ALG bind(%s): hash not available. "
+				"See /proc/crypto hash algorithm list.\n",
+				alg);
+		else
+			fprintf(stderr, "AF_ALG bind(%s): %s\n",
+				alg, strerror(errno));
+		return 1;
+	}
+
+	outfd = accept(sfd, NULL, 0);
+	if (outfd < 0) {
+		perror("AF_ALG accept");
+		return 1;
+	}
+
+	if (setup_context(QD, &ring))
+		return 1;
+	if (get_file_size(infd, &insize))
+		return 1;
+
+	ret = digest_file(&ring, insize);
+	if (ret) {
+		fprintf(stderr, "%s digest failed\n", alg);
+		return 1;
+	}
+
+	ret = get_result(&ring, alg, infile);
+	if (ret) {
+		fprintf(stderr, "failed to retrieve %s digest result\n", alg);
+		return 1;
+	}
+
+	if (close(infd) < 0)
+		ret |= 1;
+	if (close(sfd) < 0)
+		ret |= 1;
+	if (close(outfd) < 0)
+		ret |= 1;
+	io_uring_queue_exit(&ring);
+	return ret;
+}