Add `zstream redup` command to convert deduplicated send streams

Deduplicated send and receive is deprecated.  To ease migration to the
new dedup-send-less world, the commit adds a `zstream redup` utility to
convert deduplicated send streams to normal streams, so that they can
continue to be received indefinitely.

The new `zstream` command also replaces the functionality of
`zstreamdump`, by way of the `zstream dump` subcommand.  The
`zstreamdump` command is replaced by a shell script which invokes
`zstream dump`.

The way that `zstream redup` works under the hood is that as we read the
send stream, we build up a hash table which maps from `<GUID, object,
offset> -> <file_offset>`.

Whenever we see a WRITE record, we add a new entry to the hash table,
which indicates where in the stream file to find the WRITE record for
this block. (The key is `drr_toguid, drr_object, drr_offset`.)

For entries other than WRITE_BYREF, we pass them through unchanged
(except for the running checksum, which is recalculated).

For WRITE_BYREF records, we change them to WRITE records.  We find the
referenced WRITE record by looking in the hash table (for the record
with key `drr_refguid, drr_refobject, drr_refoffset`), and then reading
the record header and payload from the specified offset in the stream
file.  This is why the stream can not be a pipe.  The found WRITE record
replaces the WRITE_BYREF record, with its `drr_toguid`, `drr_object`,
and `drr_offset` fields changed to be the same as the WRITE_BYREF's
(i.e. we are writing the same logical block, but with the data supplied
by the previous WRITE record).

This algorithm requires memory proportional to the number of WRITE
records (same as `zfs send -D`), but the size per WRITE record is
relatively low (40 bytes, vs. 72 for `zfs send -D`).  A 1TB send stream
with 8KB blocks (`recordsize=8k`) would use around 5GB of RAM to
"redup".

Reviewed-by: Jorgen Lundman <[email protected]>
Reviewed-by: Paul Dagnelie <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Matthew Ahrens <[email protected]>
Closes #10124 
Closes #10156 

16 files changed, 728 insertions, 36 deletions

diff --git a/cmd/Makefile.am b/cmd/Makefile.am
index 90270209b..2078bc13b 100644
--- a/cmd/Makefile.am
+++ b/cmd/Makefile.am
@@ -1,4 +1,4 @@
-SUBDIRS  = zfs zpool zdb zhack zinject zstreamdump ztest
+SUBDIRS  = zfs zpool zdb zhack zinject zstream zstreamdump ztest
 SUBDIRS += fsck_zfs vdev_id raidz_test zgenhostid
 
 if USING_PYTHON
diff --git a/cmd/zstream/.gitignore b/cmd/zstream/.gitignore
new file mode 100644
index 000000000..fd1240d55
--- /dev/null
+++ b/cmd/zstream/.gitignore
@@ -0,0 +1 @@
+zstream
diff --git a/cmd/zstream/Makefile.am b/cmd/zstream/Makefile.am
new file mode 100644
index 000000000..892e15830
--- /dev/null
+++ b/cmd/zstream/Makefile.am
@@ -0,0 +1,13 @@
+include $(top_srcdir)/config/Rules.am
+
+sbin_PROGRAMS = zstream
+
+zstream_SOURCES = \
+	zstream.c \
+	zstream.h \
+	zstream_dump.c \
+	zstream_redup.c
+
+zstream_LDADD = \
+	$(top_builddir)/lib/libnvpair/libnvpair.la \
+	$(top_builddir)/lib/libzfs/libzfs.la
diff --git a/cmd/zstream/zstream.c b/cmd/zstream/zstream.c
new file mode 100644
index 000000000..95578c97c
--- /dev/null
+++ b/cmd/zstream/zstream.c
@@ -0,0 +1,61 @@
+/*
+ * CDDL HEADER START
+ *
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2020 by Delphix. All rights reserved.
+ */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <strings.h>
+#include <unistd.h>
+#include <libintl.h>
+#include <stddef.h>
+#include <libzfs.h>
+#include "zstream.h"
+
+void
+zstream_usage(void)
+{
+	(void) fprintf(stderr,
+	    "usage: zstream command args ...\n"
+	    "Available commands are:\n"
+	    "\n"
+	    "\tzstream dump [-vCd] FILE\n"
+	    "\t... | zstream dump [-vCd]\n"
+	    "\n"
+	    "\tzstream redup [-v] FILE | ...\n");
+	exit(1);
+}
+
+int
+main(int argc, char *argv[])
+{
+	if (argc < 2)
+		zstream_usage();
+
+	char *subcommand = argv[1];
+
+	if (strcmp(subcommand, "dump") == 0) {
+		return (zstream_do_dump(argc - 1, argv + 1));
+	} else if (strcmp(subcommand, "redup") == 0) {
+		return (zstream_do_redup(argc - 1, argv + 1));
+	} else {
+		zstream_usage();
+	}
+}
diff --git a/cmd/zstream/zstream.h b/cmd/zstream/zstream.h
new file mode 100644
index 000000000..5a7f4bce9
--- /dev/null
+++ b/cmd/zstream/zstream.h
@@ -0,0 +1,35 @@
+/*
+ * CDDL HEADER START
+ *
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2020 by Delphix. All rights reserved.
+ */
+
+#ifndef	_ZSTREAM_H
+#define	_ZSTREAM_H
+
+#ifdef	__cplusplus
+extern "C" {
+#endif
+
+extern int zstream_do_redup(int, char *[]);
+extern int zstream_do_dump(int, char *[]);
+extern void zstream_usage(void);
+
+#ifdef	__cplusplus
+}
+#endif
+
+#endif	/* _ZSTREAM_H */
diff --git a/cmd/zstreamdump/zstreamdump.c b/cmd/zstream/zstream_dump.c
index ad3cefafc..62a1d8272 100644
--- a/cmd/zstreamdump/zstreamdump.c
+++ b/cmd/zstream/zstream_dump.c
@@ -42,6 +42,7 @@
 #include <sys/zfs_ioctl.h>
 #include <sys/zio.h>
 #include <zfs_fletcher.h>
+#include "zstream.h"
 
 /*
  * If dump mode is enabled, the number of bytes to print per line
@@ -58,17 +59,6 @@ FILE *send_stream = 0;
 boolean_t do_byteswap = B_FALSE;
 boolean_t do_cksum = B_TRUE;
 
-static void
-usage(void)
-{
-	(void) fprintf(stderr, "usage: zstreamdump [-v] [-C] [-d] < file\n");
-	(void) fprintf(stderr, "\t -v -- verbose\n");
-	(void) fprintf(stderr, "\t -C -- suppress checksum verification\n");
-	(void) fprintf(stderr, "\t -d -- dump contents of blocks modified, "
-	    "implies verbose\n");
-	exit(1);
-}
-
 static void *
 safe_malloc(size_t size)
 {
@@ -215,7 +205,7 @@ sprintf_bytes(char *str, uint8_t *buf, uint_t buf_len)
 }
 
 int
-main(int argc, char *argv[])
+zstream_do_dump(int argc, char *argv[])
 {
 	char *buf = safe_malloc(SPA_MAXBLOCKSIZE);
 	uint64_t drr_record_count[DRR_NUMTYPES] = { 0 };
@@ -273,26 +263,39 @@ main(int argc, char *argv[])
 		case ':':
 			(void) fprintf(stderr,
 			    "missing argument for '%c' option\n", optopt);
-			usage();
+			zstream_usage();
 			break;
 		case '?':
 			(void) fprintf(stderr, "invalid option '%c'\n",
 			    optopt);
-			usage();
+			zstream_usage();
 			break;
 		}
 	}
 
-	if (isatty(STDIN_FILENO)) {
-		(void) fprintf(stderr,
-		    "Error: Backup stream can not be read "
-		    "from a terminal.\n"
-		    "You must redirect standard input.\n");
-		exit(1);
+	if (argc > optind) {
+		const char *filename = argv[optind];
+		send_stream = fopen(filename, "r");
+		if (send_stream == NULL) {
+			(void) fprintf(stderr,
+			    "Error while opening file '%s': %s\n",
+			    filename, strerror(errno));
+			exit(1);
+		}
+	} else {
+		if (isatty(STDIN_FILENO)) {
+			(void) fprintf(stderr,
+			    "Error: The send stream is a binary format "
+			    "and can not be read from a\n"
+			    "terminal.  Standard input must be redirected, "
+			    "or a file must be\n"
+			    "specified as a command-line argument.\n");
+			exit(1);
+		}
+		send_stream = stdin;
 	}
 
 	fletcher_4_init();
-	send_stream = stdin;
 	while (read_hdr(drr, &zc)) {
 
 		/*
diff --git a/cmd/zstream/zstream_redup.c b/cmd/zstream/zstream_redup.c
new file mode 100644
index 000000000..6720cfd12
--- /dev/null
+++ b/cmd/zstream/zstream_redup.c
@@ -0,0 +1,468 @@
+/*
+ * CDDL HEADER START
+ *
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2020 by Delphix. All rights reserved.
+ */
+
+#include <assert.h>
+#include <cityhash.h>
+#include <ctype.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <libzfs_impl.h>
+#include <libzfs.h>
+#include <libzutil.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <strings.h>
+#include <umem.h>
+#include <unistd.h>
+#include <sys/debug.h>
+#include <sys/stat.h>
+#include <sys/zfs_ioctl.h>
+#include <sys/zio_checksum.h>
+#include "zfs_fletcher.h"
+#include "zstream.h"
+
+
+#define	MAX_RDT_PHYSMEM_PERCENT		20
+#define	SMALLEST_POSSIBLE_MAX_RDT_MB		128
+
+typedef struct redup_entry {
+	struct redup_entry	*rde_next;
+	uint64_t rde_guid;
+	uint64_t rde_object;
+	uint64_t rde_offset;
+	uint64_t rde_stream_offset;
+} redup_entry_t;
+
+typedef struct redup_table {
+	redup_entry_t	**redup_hash_array;
+	umem_cache_t	*ddecache;
+	uint64_t	ddt_count;
+	int		numhashbits;
+} redup_table_t;
+
+int
+highbit64(uint64_t i)
+{
+	if (i == 0)
+		return (0);
+
+	return (NBBY * sizeof (uint64_t) - __builtin_clzll(i));
+}
+
+static void *
+safe_calloc(size_t n)
+{
+	void *rv = calloc(1, n);
+	if (rv == NULL) {
+		fprintf(stderr,
+		    "Error: could not allocate %u bytes of memory\n",
+		    (int)n);
+		exit(1);
+	}
+	return (rv);
+}
+
+/*
+ * Safe version of fread(), exits on error.
+ */
+static int
+sfread(void *buf, size_t size, FILE *fp)
+{
+	int rv = fread(buf, size, 1, fp);
+	if (rv == 0 && ferror(fp)) {
+		(void) fprintf(stderr, "Error while reading file: %s\n",
+		    strerror(errno));
+		exit(1);
+	}
+	return (rv);
+}
+
+/*
+ * Safe version of pread(), exits on error.
+ */
+static void
+spread(int fd, void *buf, size_t count, off_t offset)
+{
+	ssize_t err = pread(fd, buf, count, offset);
+	if (err == -1) {
+		(void) fprintf(stderr,
+		    "Error while reading file: %s\n",
+		    strerror(errno));
+		exit(1);
+	} else if (err != count) {
+		(void) fprintf(stderr,
+		    "Error while reading file: short read\n");
+		exit(1);
+	}
+}
+
+static int
+dump_record(dmu_replay_record_t *drr, void *payload, int payload_len,
+    zio_cksum_t *zc, int outfd)
+{
+	assert(offsetof(dmu_replay_record_t, drr_u.drr_checksum.drr_checksum)
+	    == sizeof (dmu_replay_record_t) - sizeof (zio_cksum_t));
+	fletcher_4_incremental_native(drr,
+	    offsetof(dmu_replay_record_t, drr_u.drr_checksum.drr_checksum), zc);
+	if (drr->drr_type != DRR_BEGIN) {
+		assert(ZIO_CHECKSUM_IS_ZERO(&drr->drr_u.
+		    drr_checksum.drr_checksum));
+		drr->drr_u.drr_checksum.drr_checksum = *zc;
+	}
+	fletcher_4_incremental_native(&drr->drr_u.drr_checksum.drr_checksum,
+	    sizeof (zio_cksum_t), zc);
+	if (write(outfd, drr, sizeof (*drr)) == -1)
+		return (errno);
+	if (payload_len != 0) {
+		fletcher_4_incremental_native(payload, payload_len, zc);
+		if (write(outfd, payload, payload_len) == -1)
+			return (errno);
+	}
+	return (0);
+}
+
+static void
+rdt_insert(redup_table_t *rdt,
+    uint64_t guid, uint64_t object, uint64_t offset, uint64_t stream_offset)
+{
+	uint64_t ch = cityhash4(guid, object, offset, 0);
+	uint64_t hashcode = BF64_GET(ch, 0, rdt->numhashbits);
+	redup_entry_t **rdepp;
+
+	rdepp = &(rdt->redup_hash_array[hashcode]);
+	redup_entry_t *rde = umem_cache_alloc(rdt->ddecache, UMEM_NOFAIL);
+	rde->rde_next = *rdepp;
+	rde->rde_guid = guid;
+	rde->rde_object = object;
+	rde->rde_offset = offset;
+	rde->rde_stream_offset = stream_offset;
+	*rdepp = rde;
+	rdt->ddt_count++;
+}
+
+static void
+rdt_lookup(redup_table_t *rdt,
+    uint64_t guid, uint64_t object, uint64_t offset,
+    uint64_t *stream_offsetp)
+{
+	uint64_t ch = cityhash4(guid, object, offset, 0);
+	uint64_t hashcode = BF64_GET(ch, 0, rdt->numhashbits);
+
+	for (redup_entry_t *rde = rdt->redup_hash_array[hashcode];
+	    rde != NULL; rde = rde->rde_next) {
+		if (rde->rde_guid == guid &&
+		    rde->rde_object == object &&
+		    rde->rde_offset == offset) {
+			*stream_offsetp = rde->rde_stream_offset;
+			return;
+		}
+	}
+	assert(!"could not find expected redup table entry");
+}
+
+/*
+ * Convert a dedup stream (generated by "zfs send -D") to a
+ * non-deduplicated stream.  The entire infd will be converted, including
+ * any substreams in a stream package (generated by "zfs send -RD"). The
+ * infd must be seekable.
+ */
+static void
+zfs_redup_stream(int infd, int outfd, boolean_t verbose)
+{
+	int bufsz = SPA_MAXBLOCKSIZE;
+	dmu_replay_record_t thedrr = { 0 };
+	dmu_replay_record_t *drr = &thedrr;
+	redup_table_t rdt;
+	zio_cksum_t stream_cksum;
+	uint64_t numbuckets;
+	uint64_t num_records = 0;
+	uint64_t num_write_byref_records = 0;
+
+#ifdef _ILP32
+	uint64_t max_rde_size = SMALLEST_POSSIBLE_MAX_RDT_MB << 20;
+#else
+	uint64_t physmem = sysconf(_SC_PHYS_PAGES) * sysconf(_SC_PAGESIZE);
+	uint64_t max_rde_size =
+	    MAX((physmem * MAX_RDT_PHYSMEM_PERCENT) / 100,
+	    SMALLEST_POSSIBLE_MAX_RDT_MB << 20);
+#endif
+
+	numbuckets = max_rde_size / (sizeof (redup_entry_t));
+
+	/*
+	 * numbuckets must be a power of 2.  Increase number to
+	 * a power of 2 if necessary.
+	 */
+	if (!ISP2(numbuckets))
+		numbuckets = 1ULL << highbit64(numbuckets);
+
+	rdt.redup_hash_array =
+	    safe_calloc(numbuckets * sizeof (redup_entry_t *));
+	rdt.ddecache = umem_cache_create("rde", sizeof (redup_entry_t), 0,
+	    NULL, NULL, NULL, NULL, NULL, 0);
+	rdt.numhashbits = highbit64(numbuckets) - 1;
+
+	char *buf = safe_calloc(bufsz);
+	FILE *ofp = fdopen(infd, "r");
+	long offset = ftell(ofp);
+	while (sfread(drr, sizeof (*drr), ofp) != 0) {
+		num_records++;
+
+		/*
+		 * We need to regenerate the checksum.
+		 */
+		if (drr->drr_type != DRR_BEGIN) {
+			bzero(&drr->drr_u.drr_checksum.drr_checksum,
+			    sizeof (drr->drr_u.drr_checksum.drr_checksum));
+		}
+
+		uint64_t payload_size = 0;
+		switch (drr->drr_type) {
+		case DRR_BEGIN:
+		{
+			struct drr_begin *drrb = &drr->drr_u.drr_begin;
+			int fflags;
+			ZIO_SET_CHECKSUM(&stream_cksum, 0, 0, 0, 0);
+
+			assert(drrb->drr_magic == DMU_BACKUP_MAGIC);
+
+			/* clear the DEDUP feature flag for this stream */
+			fflags = DMU_GET_FEATUREFLAGS(drrb->drr_versioninfo);
+			fflags &= ~(DMU_BACKUP_FEATURE_DEDUP |
+			    DMU_BACKUP_FEATURE_DEDUPPROPS);
+			DMU_SET_FEATUREFLAGS(drrb->drr_versioninfo, fflags);
+
+			int sz = drr->drr_payloadlen;
+			if (sz != 0) {
+				if (sz > bufsz) {
+					free(buf);
+					buf = safe_calloc(sz);
+					bufsz = sz;
+				}
+				(void) sfread(buf, sz, ofp);
+			}
+			payload_size = sz;
+			break;
+		}
+
+		case DRR_END:
+		{
+			struct drr_end *drre = &drr->drr_u.drr_end;
+			/*
+			 * Use the recalculated checksum, unless this is
+			 * the END record of a stream package, which has
+			 * no checksum.
+			 */
+			if (!ZIO_CHECKSUM_IS_ZERO(&drre->drr_checksum))
+				drre->drr_checksum = stream_cksum;
+			break;
+		}
+
+		case DRR_OBJECT:
+		{
+			struct drr_object *drro = &drr->drr_u.drr_object;
+
+			if (drro->drr_bonuslen > 0) {
+				payload_size = DRR_OBJECT_PAYLOAD_SIZE(drro);
+				(void) sfread(buf, payload_size, ofp);
+			}
+			break;
+		}
+
+		case DRR_SPILL:
+		{
+			struct drr_spill *drrs = &drr->drr_u.drr_spill;
+			payload_size = DRR_SPILL_PAYLOAD_SIZE(drrs);
+			(void) sfread(buf, payload_size, ofp);
+			break;
+		}
+
+		case DRR_WRITE_BYREF:
+		{
+			struct drr_write_byref drrwb =
+			    drr->drr_u.drr_write_byref;
+
+			num_write_byref_records++;
+
+			/*
+			 * Look up in hash table by drrwb->drr_refguid,
+			 * drr_refobject, drr_refoffset.  Replace this
+			 * record with the found WRITE record, but with
+			 * drr_object,drr_offset,drr_toguid replaced with ours.
+			 */
+			uint64_t stream_offset;
+			rdt_lookup(&rdt, drrwb.drr_refguid,
+			    drrwb.drr_refobject, drrwb.drr_refoffset,
+			    &stream_offset);
+
+			spread(infd, drr, sizeof (*drr), stream_offset);
+
+			assert(drr->drr_type == DRR_WRITE);
+			struct drr_write *drrw = &drr->drr_u.drr_write;
+			assert(drrw->drr_toguid == drrwb.drr_refguid);
+			assert(drrw->drr_object == drrwb.drr_refobject);
+			assert(drrw->drr_offset == drrwb.drr_refoffset);
+
+			payload_size = DRR_WRITE_PAYLOAD_SIZE(drrw);
+			spread(infd, buf, payload_size,
+			    stream_offset + sizeof (*drr));
+
+			drrw->drr_toguid = drrwb.drr_toguid;
+			drrw->drr_object = drrwb.drr_object;
+			drrw->drr_offset = drrwb.drr_offset;
+			break;
+		}
+
+		case DRR_WRITE:
+		{
+			struct drr_write *drrw = &drr->drr_u.drr_write;
+			payload_size = DRR_WRITE_PAYLOAD_SIZE(drrw);
+			(void) sfread(buf, payload_size, ofp);
+
+			rdt_insert(&rdt, drrw->drr_toguid,
+			    drrw->drr_object, drrw->drr_offset, offset);
+			break;
+		}
+
+		case DRR_WRITE_EMBEDDED:
+		{
+			struct drr_write_embedded *drrwe =
+			    &drr->drr_u.drr_write_embedded;
+			payload_size =
+			    P2ROUNDUP((uint64_t)drrwe->drr_psize, 8);
+			(void) sfread(buf, payload_size, ofp);
+			break;
+		}
+
+		case DRR_FREEOBJECTS:
+		case DRR_FREE:
+		case DRR_OBJECT_RANGE:
+			break;
+
+		default:
+			(void) fprintf(stderr, "INVALID record type 0x%x\n",
+			    drr->drr_type);
+			/* should never happen, so assert */
+			assert(B_FALSE);
+		}
+
+		if (feof(ofp)) {
+			fprintf(stderr, "Error: unexpected end-of-file\n");
+			exit(1);
+		}
+		if (ferror(ofp)) {
+			fprintf(stderr, "Error while reading file: %s\n",
+			    strerror(errno));
+			exit(1);
+		}
+
+		/*
+		 * We need to recalculate the checksum, and it needs to be
+		 * initially zero to do that.  BEGIN records don't have
+		 * a checksum.
+		 */
+		if (drr->drr_type != DRR_BEGIN) {
+			bzero(&drr->drr_u.drr_checksum.drr_checksum,
+			    sizeof (drr->drr_u.drr_checksum.drr_checksum));
+		}
+		if (dump_record(drr, buf, payload_size,
+		    &stream_cksum, outfd) != 0)
+			break;
+		if (drr->drr_type == DRR_END) {
+			/*
+			 * Typically the END record is either the last
+			 * thing in the stream, or it is followed
+			 * by a BEGIN record (which also zeros the checksum).
+			 * However, a stream package ends with two END
+			 * records.  The last END record's checksum starts
+			 * from zero.
+			 */
+			ZIO_SET_CHECKSUM(&stream_cksum, 0, 0, 0, 0);
+		}
+		offset = ftell(ofp);
+	}
+
+	if (verbose) {
+		char mem_str[16];
+		zfs_nicenum(rdt.ddt_count * sizeof (redup_entry_t),
+		    mem_str, sizeof (mem_str));
+		fprintf(stderr, "converted stream with %llu total records, "
+		    "including %llu dedup records, using %sB memory.\n",
+		    (long long)num_records,
+		    (long long)num_write_byref_records,
+		    mem_str);
+	}
+
+	umem_cache_destroy(rdt.ddecache);
+	free(rdt.redup_hash_array);
+	free(buf);
+	(void) fclose(ofp);
+}
+
+int
+zstream_do_redup(int argc, char *argv[])
+{
+	boolean_t verbose = B_FALSE;
+	char c;
+
+	while ((c = getopt(argc, argv, "v")) != -1) {
+		switch (c) {
+		case 'v':
+			verbose = B_TRUE;
+			break;
+		case '?':
+			(void) fprintf(stderr, "invalid option '%c'\n",
+			    optopt);
+			zstream_usage();
+			break;
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	if (argc != 1)
+		zstream_usage();
+
+	const char *filename = argv[0];
+
+	if (isatty(STDOUT_FILENO)) {
+		(void) fprintf(stderr,
+		    "Error: Stream can not be written to a terminal.\n"
+		    "You must redirect standard output.\n");
+		return (1);
+	}
+
+	int fd = open(filename, O_RDONLY);
+	if (fd == -1) {
+		(void) fprintf(stderr,
+		    "Error while opening file '%s': %s\n",
+		    filename, strerror(errno));
+		exit(1);
+	}
+
+	fletcher_4_init();
+	zfs_redup_stream(fd, STDOUT_FILENO, verbose);
+	fletcher_4_fini();
+
+	close(fd);
+
+	return (0);
+}
diff --git a/cmd/zstreamdump/Makefile.am b/cmd/zstreamdump/Makefile.am
index 1f5cd4d9f..2c04d8513 100644
--- a/cmd/zstreamdump/Makefile.am
+++ b/cmd/zstreamdump/Makefile.am
@@ -1,10 +1 @@
-include $(top_srcdir)/config/Rules.am
-
-sbin_PROGRAMS = zstreamdump
-
-zstreamdump_SOURCES = \
-	zstreamdump.c
-
-zstreamdump_LDADD = \
-	$(top_builddir)/lib/libnvpair/libnvpair.la \
-	$(top_builddir)/lib/libzfs/libzfs.la
+dist_sbin_SCRIPTS = zstreamdump
diff --git a/cmd/zstreamdump/zstreamdump b/cmd/zstreamdump/zstreamdump
new file mode 100755
index 000000000..fbf02ee68
--- /dev/null
+++ b/cmd/zstreamdump/zstreamdump
@@ -0,0 +1,3 @@
+#!/bin/sh
+
+zstream dump "$@"
diff --git a/configure.ac b/configure.ac
index 8604cdaa5..7522940d2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -80,6 +80,7 @@ AC_CONFIG_FILES([
 	cmd/zhack/Makefile
 	cmd/zinject/Makefile
 	cmd/zpool/Makefile
+	cmd/zstream/Makefile
 	cmd/zstreamdump/Makefile
 	cmd/ztest/Makefile
 	cmd/zvol_id/Makefile
diff --git a/lib/libzfs/libzfs_sendrecv.c b/lib/libzfs/libzfs_sendrecv.c
index 138d1ba08..43a39e789 100644
--- a/lib/libzfs/libzfs_sendrecv.c
+++ b/lib/libzfs/libzfs_sendrecv.c
@@ -61,6 +61,7 @@
 #include "zfs_prop.h"
 #include "zfs_fletcher.h"
 #include "libzfs_impl.h"
+#include <cityhash.h>
 #include <zlib.h>
 #include <sys/zio_checksum.h>
 #include <sys/dsl_crypt.h>
@@ -5518,9 +5519,7 @@ zfs_receive_impl(libzfs_handle_t *hdl, const char *tosnap,
 	}
 
 	/* Holds feature is set once in the compound stream header. */
-	boolean_t holds = (DMU_GET_FEATUREFLAGS(drrb->drr_versioninfo) &
-	    DMU_BACKUP_FEATURE_HOLDS);
-	if (holds)
+	if (featureflags & DMU_BACKUP_FEATURE_HOLDS)
 		flags->holds = B_TRUE;
 
 	if (strchr(drrb->drr_toname, '@') == NULL) {
diff --git a/man/man8/Makefile.am b/man/man8/Makefile.am
index 8239c2157..b7d26570e 100644
--- a/man/man8/Makefile.am
+++ b/man/man8/Makefile.am
@@ -78,6 +78,7 @@ dist_man_MANS = \
 	zpool-trim.8 \
 	zpool-upgrade.8 \
 	zpool-wait.8 \
+	zstream.8 \
 	zstreamdump.8
 
 nodist_man_MANS = \
diff --git a/man/man8/zstream.8 b/man/man8/zstream.8
new file mode 100644
index 000000000..1c4d3fa9a
--- /dev/null
+++ b/man/man8/zstream.8
@@ -0,0 +1,101 @@
+.\"
+.\" CDDL HEADER START
+.\"
+.\" The contents of this file are subject to the terms of the
+.\" Common Development and Distribution License (the "License").
+.\" You may not use this file except in compliance with the License.
+.\"
+.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+.\" or http://www.opensolaris.org/os/licensing.
+.\" See the License for the specific language governing permissions
+.\" and limitations under the License.
+.\"
+.\" When distributing Covered Code, include this CDDL HEADER in each
+.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+.\" If applicable, add the following below this CDDL HEADER, with the
+.\" fields enclosed by brackets "[]" replaced with your own identifying
+.\" information: Portions Copyright [yyyy] [name of copyright owner]
+.\"
+.\" CDDL HEADER END
+.\"
+.\"
+.\" Copyright (c) 2020 by Delphix. All rights reserved.
+.Dd March 25, 2020
+.Dt ZSTREAM 8
+.Os Linux
+.Sh NAME
+.Nm zstream
+.Nd manipulate zfs send streams
+.Sh SYNOPSIS
+.Nm
+.Cm dump
+.Op Fl Cvd
+.Op Ar file
+.Nm
+.Cm redup
+.Op Fl v
+.Ar file
+.Sh DESCRIPTION
+.sp
+.LP
+The
+.Sy zstream
+utility manipulates zfs send streams, which are the output of the
+.Sy zfs send
+command.
+.Bl -tag -width ""
+.It Xo
+.Nm
+.Cm dump
+.Op Fl Cvd
+.Op Ar file
+.Xc
+Print information about the specified send stream, including headers and
+record counts.
+The send stream may either be in the specified
+.Ar file ,
+or provided on standard input.
+.Bl -tag -width "-D"
+.It Fl C
+Suppress the validation of checksums.
+.It Fl v
+Verbose.
+Print metadata for each record.
+.It Fl d
+Dump data contained in each record.
+Implies verbose.
+.El
+.It Xo
+.Nm
+.Cm redup
+.Op Fl v
+.Ar file
+.Xc
+Deduplicated send streams can be generated by using the
+.Nm zfs Cm send Fl D
+command.
+The ability to send deduplicated send streams is deprecated.
+In the future, the ability to receive a deduplicated send stream with
+.Nm zfs Cm receive
+will be removed.
+However, deduplicated send streams can still be received by utilizing
+.Nm zstream Cm redup .
+.Pp
+The
+.Nm zstream Cm redup
+command is provided a
+.Ar file
+containing a deduplicated send stream, and outputs an equivalent
+non-deduplicated send stream on standard output.
+Therefore, a deduplicated send stream can be received by running:
+.Bd -literal
+# zstream redup DEDUP_STREAM_FILE | zfs receive ...
+.Ed
+.Bl -tag -width "-D"
+.It Fl v
+Verbose.
+Print summary of converted records.
+.Sh SEE ALSO
+.Xr zfs 8 ,
+.Xr zfs-send 8 ,
+.Xr zfs-receive 8
diff --git a/tests/zfs-tests/include/commands.cfg b/tests/zfs-tests/include/commands.cfg
index 4498f1a53..cf65313ac 100644
--- a/tests/zfs-tests/include/commands.cfg
+++ b/tests/zfs-tests/include/commands.cfg
@@ -182,6 +182,7 @@ export ZFS_FILES='zdb
     dbufstat
     zed
     zgenhostid
+    zstream
     zstreamdump'
 
 export ZFSTEST_FILES='btree_test
diff --git a/tests/zfs-tests/tests/functional/cli_root/zfs_receive/zfs_receive_013_pos.ksh b/tests/zfs-tests/tests/functional/cli_root/zfs_receive/zfs_receive_013_pos.ksh
index 5d7a7043b..be8f49809 100755
--- a/tests/zfs-tests/tests/functional/cli_root/zfs_receive/zfs_receive_013_pos.ksh
+++ b/tests/zfs-tests/tests/functional/cli_root/zfs_receive/zfs_receive_013_pos.ksh
@@ -67,6 +67,8 @@ zfs snapshot $src_fs@snap3
 
 log_must eval "zfs send -D -R $src_fs@snap3 > $streamfile"
 log_must eval "zfs receive -v $dst_fs < $streamfile"
+log_must zfs destroy -r $dst_fs
+log_must eval "zstream redup $streamfile | zfs receive -v $dst_fs"
 
 cleanup
 
diff --git a/tests/zfs-tests/tests/functional/rsend/send-cD.ksh b/tests/zfs-tests/tests/functional/rsend/send-cD.ksh
index 97db0a7c2..fcbec2d9e 100755
--- a/tests/zfs-tests/tests/functional/rsend/send-cD.ksh
+++ b/tests/zfs-tests/tests/functional/rsend/send-cD.ksh
@@ -64,14 +64,26 @@ typeset size0=$(stat_size $stream0)
 typeset size1=$(stat_size $stream1)
 within_percent $size0 $size1 90 || log_fail "$size0 and $size1"
 
-# Finally, make sure the receive works correctly.
+# make sure the receive works correctly.
 log_must eval "zfs send -D -c -i snap0 $sendfs@snap1 >$inc"
 log_must eval "zfs recv -d $recvfs <$stream0"
 log_must eval "zfs recv -d $recvfs <$inc"
 cmp_ds_cont $sendfs $recvfs
 
+# check receive with redup.
+log_must zfs destroy -r $recvfs
+log_must zfs create -o compress=lz4 $recvfs
+log_must eval "zstream redup $stream0 | zfs recv -d $recvfs"
+log_must eval "zstream redup $inc | zfs recv -d $recvfs"
+cmp_ds_cont $sendfs $recvfs
+
 # The size of the incremental should be the same as the initial send.
 typeset size2=$(stat_size $inc)
 within_percent $size0 $size2 90 || log_fail "$size0 and $size1"
 
+# The redup'ed size should be 4x
+typeset size3=$(zstream redup $inc | wc -c)
+let size4=size0*4
+within_percent $size4 $size3 90 || log_fail "$size4 and $size3"
+
 log_pass "The -c and -D flags do not interfere with each other"