5 files changed, 104 insertions, 22 deletions

diff --git a/sbin/restore/main.c b/sbin/restore/main.c
index 63fb4efd347d..91f4a83c7296 100644
--- a/sbin/restore/main.c
+++ b/sbin/restore/main.c
@@ -60,7 +60,7 @@ __FBSDID("$FreeBSD$");
 #include "restore.h"
 #include "extern.h"
 
-int	bflag = 0, cvtflag = 0, dflag = 0, vflag = 0, yflag = 0;
+int	bflag = 0, cvtflag = 0, dflag = 0, Dflag = 0, vflag = 0, yflag = 0;
 int	hflag = 1, mflag = 1, Nflag = 0;
 int	uflag = 0;
 int	pipecmd = 0;
@@ -97,7 +97,7 @@ main(int argc, char *argv[])
 
 	inputdev = NULL;
 	obsolete(&argc, &argv);
-	while ((ch = getopt(argc, argv, "b:df:himNP:Rrs:tuvxy")) != -1)
+	while ((ch = getopt(argc, argv, "b:dDf:himNP:Rrs:tuvxy")) != -1)
 		switch(ch) {
 		case 'b':
 			/* Change default tape blocksize. */
@@ -111,6 +111,9 @@ main(int argc, char *argv[])
 		case 'd':
 			dflag = 1;
 			break;
+		case 'D':
+			Dflag = 1;
+			break;
 		case 'f':
 			if (pipecmd)
 				errx(1,
diff --git a/sbin/restore/restore.8 b/sbin/restore/restore.8
index 9db0d67870da..cf6a364693b0 100644
--- a/sbin/restore/restore.8
+++ b/sbin/restore/restore.8
@@ -38,32 +38,32 @@
 .Sh SYNOPSIS
 .Nm
 .Fl i
-.Op Fl dhmNuvy
+.Op Fl dDhmNuvy
 .Op Fl b Ar blocksize
 .Op Fl f Ar file | Fl P Ar pipecommand
 .Op Fl s Ar fileno
 .Nm
 .Fl R
-.Op Fl dNuvy
+.Op Fl dDNuvy
 .Op Fl b Ar blocksize
 .Op Fl f Ar file | Fl P Ar pipecommand
 .Op Fl s Ar fileno
 .Nm
 .Fl r
-.Op Fl dNuvy
+.Op Fl dDNuvy
 .Op Fl b Ar blocksize
 .Op Fl f Ar file | Fl P Ar pipecommand
 .Op Fl s Ar fileno
 .Nm
 .Fl t
-.Op Fl dhNuvy
+.Op Fl dDhNuvy
 .Op Fl b Ar blocksize
 .Op Fl f Ar file | Fl P Ar pipecommand
 .Op Fl s Ar fileno
 .Op Ar
 .Nm
 .Fl x
-.Op Fl dhmNuvy
+.Op Fl dDhmNuvy
 .Op Fl b Ar blocksize
 .Op Fl f Ar file | Fl P Ar pipecommand
 .Op Fl s Ar fileno
@@ -278,6 +278,12 @@ option is not specified,
 tries to determine the media block size dynamically.
 .It Fl d
 Sends verbose debugging output to the standard error.
+.It Fl D
+This puts
+.Nm
+into degraded mode,
+causing restore to operate less efficiently
+but to try harder to read corrupted backups.
 .It Fl f Ar file
 Read the backup from
 .Ar file ;
diff --git a/sbin/restore/restore.c b/sbin/restore/restore.c
index 046c0d27afc2..e494cdb69a7d 100644
--- a/sbin/restore/restore.c
+++ b/sbin/restore/restore.c
@@ -687,6 +687,17 @@ createfiles(void)
 		 */
 		if (first > last)
 			return;
+		if (Dflag) {
+			if (curfile.ino == maxino)
+				return;
+			if((ep = lookupino(curfile.ino)) != NULL &&
+			    (ep->e_flags & (NEW|EXTRACT))) {
+				goto justgetit;
+			} else {
+				skipfile();
+				continue;
+			}
+		}
 		/*
 		 * Reject any volumes with inodes greater than the last
 		 * one needed, so that we can quickly skip backwards to
@@ -749,6 +760,7 @@ createfiles(void)
 			ep = lookupino(next);
 			if (ep == NULL)
 				panic("corrupted symbol table\n");
+justgetit:
 			(void) extractfile(myname(ep));
 			ep->e_flags &= ~NEW;
 			if (volno != curvol)
diff --git a/sbin/restore/restore.h b/sbin/restore/restore.h
index 04048dc5de19..43e4db5acb5d 100644
--- a/sbin/restore/restore.h
+++ b/sbin/restore/restore.h
@@ -40,6 +40,7 @@
  */
 extern int	bflag;		/* set input block size */
 extern int	dflag;		/* print out debugging info */
+extern int	Dflag;		/* degraded mode - try hard to get stuff back */
 extern int	hflag;		/* restore heirarchies */
 extern int	mflag;		/* restore by name instead of inode number */
 extern int	Nflag;		/* do not write the disk */
diff --git a/sbin/restore/tape.c b/sbin/restore/tape.c
index 83f5ec879909..eb9802f07535 100644
--- a/sbin/restore/tape.c
+++ b/sbin/restore/tape.c
@@ -54,6 +54,7 @@ __FBSDID("$FreeBSD$");
 #include <limits.h>
 #include <paths.h>
 #include <setjmp.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -74,6 +75,7 @@ static int	blkcnt;
 static int	numtrec;
 static char	*tapebuf;
 static union	u_spcl endoftapemark;
+static long	byteslide = 0;
 static long	blksread;		/* blocks read since last header */
 static int64_t	tapeaddr = 0;		/* current TP_BSIZE tape record */
 static long	tapesread;
@@ -170,12 +172,13 @@ newtapebuf(long size)
 	if (size <= tapebufsize)
 		return;
 	if (tapebuf != NULL)
-		free(tapebuf);
-	tapebuf = malloc(size * TP_BSIZE);
+		free(tapebuf - TP_BSIZE);
+	tapebuf = malloc((size+1) * TP_BSIZE);
 	if (tapebuf == NULL) {
 		fprintf(stderr, "Cannot allocate space for tape buffer\n");
 		done(1);
 	}
+	tapebuf += TP_BSIZE;
 	tapebufsize = size;
 }
 
@@ -733,6 +736,15 @@ getfile(void (*fill)(char *, long), void (*skip)(char *, long))
 	gettingfile++;
 loop:
 	for (i = 0; i < spcl.c_count; i++) {
+		if (!readmapflag && i > TP_NINDIR) {
+			if (Dflag) {
+				fprintf(stderr, "spcl.c_count = %jd\n",
+				    (intmax_t)spcl.c_count);
+				break;
+			} else
+				panic("spcl.c_count = %jd\n",
+				    (intmax_t)spcl.c_count);
+		}
 		if (readmapflag || spcl.c_addr[i]) {
 			readtape(&buf[curblk++][0]);
 			if (curblk == fssize / TP_BSIZE) {
@@ -751,9 +763,20 @@ loop:
 				TP_BSIZE : size));
 		}
 		if ((size -= TP_BSIZE) <= 0) {
-			for (i++; i < spcl.c_count; i++)
+			for (i++; i < spcl.c_count; i++) {
+				if (!readmapflag && i > TP_NINDIR) {
+					if (Dflag) {
+						fprintf(stderr,
+						    "spcl.c_count = %jd\n",
+						    (intmax_t)spcl.c_count);
+						break;
+					} else 
+						panic("spcl.c_count = %jd\n",
+						    (intmax_t)spcl.c_count);
+				}
 				if (readmapflag || spcl.c_addr[i])
 					readtape(junk);
+			}
 			break;
 		}
 	}
@@ -872,15 +895,19 @@ xtrnull(char *buf, long size)
 static void
 readtape(char *buf)
 {
-	long rd, newvol, i;
+	long rd, newvol, i, oldnumtrec;
 	int cnt, seek_failed;
 
-	if (blkcnt < numtrec) {
-		memmove(buf, &tapebuf[(blkcnt++ * TP_BSIZE)], (long)TP_BSIZE);
+	if (blkcnt + (byteslide > 0) < numtrec) {
+		memmove(buf, &tapebuf[(blkcnt++ * TP_BSIZE) + byteslide], (long)TP_BSIZE);
 		blksread++;
 		tapeaddr++;
 		return;
 	}
+	if (numtrec > 0)
+		memmove(&tapebuf[-TP_BSIZE],
+		    &tapebuf[(numtrec-1) * TP_BSIZE], (long)TP_BSIZE);
+	oldnumtrec = numtrec;
 	for (i = 0; i < ntrec; i++)
 		((struct s_spcl *)&tapebuf[i * TP_BSIZE])->c_magic = 0;
 	if (numtrec == 0)
@@ -981,8 +1008,12 @@ getmore:
 		terminateinput();
 		memmove(&tapebuf[rd], &endoftapemark, (long)TP_BSIZE);
 	}
-	blkcnt = 0;
-	memmove(buf, &tapebuf[(blkcnt++ * TP_BSIZE)], (long)TP_BSIZE);
+	if (oldnumtrec == 0)
+		blkcnt = 0;
+	else
+		blkcnt -= oldnumtrec;
+	memmove(buf,
+	    &tapebuf[(blkcnt++ * TP_BSIZE) + byteslide], (long)TP_BSIZE);
 	blksread++;
 	tapeaddr++;
 }
@@ -1069,6 +1100,8 @@ gethead(struct s_spcl *buf)
 	}
 	if (checksum((int *)buf) == FAIL)
 		return (FAIL);
+	if (_time64_to_time(buf->c_date) != dumpdate)
+		fprintf(stderr, "Header with wrong dumpdate.\n");
 	if (Bcvt) {
 		swabst((u_char *)"8l4s1q8l2q17l", (u_char *)buf);
 		swabst((u_char *)"l",(u_char *) &buf->c_level);
@@ -1225,8 +1258,17 @@ findinode(struct s_spcl *header)
 				if (header->c_addr[i])
 					readtape(buf);
 			while (gethead(header) == FAIL ||
-			    _time64_to_time(header->c_date) != dumpdate)
+			    _time64_to_time(header->c_date) != dumpdate) {
 				skipcnt++;
+				if (Dflag) {
+					byteslide++;
+					if (byteslide < TP_BSIZE) {
+						blkcnt--;
+						blksread--;
+					} else 
+						byteslide = 0;
+				}
+			}
 			break;
 
 		case TS_INODE:
@@ -1263,18 +1305,36 @@ findinode(struct s_spcl *header)
 			break;
 
 		case TS_TAPE:
-			panic("unexpected tape header\n");
-			/* NOTREACHED */
+			if (Dflag)
+				fprintf(stderr, "unexpected tape header\n");
+			else
+				panic("unexpected tape header\n");
 
 		default:
-			panic("unknown tape header type %d\n", spcl.c_type);
-			/* NOTREACHED */
+			if (Dflag)
+				fprintf(stderr, "unknown tape header type %d\n",
+				    spcl.c_type);
+			else
+				panic("unknown tape header type %d\n",
+				    spcl.c_type);
+			while (gethead(header) == FAIL ||
+			    _time64_to_time(header->c_date) != dumpdate) {
+				skipcnt++;
+				if (Dflag) {
+					byteslide++;
+					if (byteslide < TP_BSIZE) {
+						blkcnt--;
+						blksread--;
+					} else 
+						byteslide = 0;
+				}
+			}
 
 		}
 	} while (htype == TS_ADDR);
 	if (skipcnt > 0)
-		fprintf(stderr, "resync restore, skipped %ld blocks\n",
-		    skipcnt);
+		fprintf(stderr, "resync restore, skipped %ld %s\n",
+		    skipcnt, Dflag ? "bytes" : "blocks");
 	skipcnt = 0;
 }