Added link hop limit to option -follow

test/xorriso.1

@@ -2,7 +2,7 @@
 .\" First parameter, NAME, should be all caps
 .\" Second parameter, SECTION, should be 1-8, maybe w/ subsection
 .\" other parameters are allowed: see man(7), man(1)
-.TH XORRISO 1 "December 15, 2007"
+.TH XORRISO 1 "December 16, 2007"
 .\" Please adjust this date whenever revising the manpage.
 .\"
 .\" Some roff macros, for reference:
@@ -667,7 +667,7 @@ SORRY event occured.
 .B Settings for data insertion:
 .TP
 \fB\-follow\fR occasion[:occasion[...]]
-Enable or disable resolution of symbolic links and mount points under
+Enable or disable resolution of symbolic links and mountpoints under
 disk_paths. This applies to actions -add, -du*x, -ls*x and to -disk_pattern
 expansion.
 .br
@@ -678,11 +678,11 @@ If enabled then symbolic links are handled as their target file objects,
 else symbolic links are handled as themselves. 
 .br
 "mount" is the hop from one filesystem to another subordinate filesystem.
-If enabled then mount point directories are handled as any other directory,
+If enabled then mountpoint directories are handled as any other directory,
-else mount points are handled as empty directories if they are encountered in
+else mountpoints are handled as empty directories if they are encountered in
 directory tree traversals.
 .br
-Less general then above occasions:
+Less general than above occasions:
 .br
 "pattern" is mount and link hopping, but only during -disk_pattern expansion.
 .br
@@ -699,9 +699,26 @@ applies.
 .br
 Shortcuts:
 .br
-"default" is equivalent to "pattern:mount".
+"default" is equivalent to "pattern:mount:limit=100".
 .br
 "on" always decides positive. Equivalent to "link:mount".
+.br
+
+Not an occasion but an optional setting is:
+.br
+"limit="<number> which sets the maximum number of link hops.
+A link hop consists of a sequence of symbolic links and a final target
+of different type. Nevertheless those hops can loop. Example:
+.br
+  \fB$\fR ln -s .. uploop
+.br
+Link hopping has a builtin loop detection which stops hopping at the first
+repetition of a link target. Then the repeated link is handled as itself
+and not as its target.
+Regrettably one can construct link networks which
+cause exponential workload before their loops get detected.
+The number given with "limit=" can curb this workload at the risk of truncating
+an intentional sequence of link hops.
 .TP
 \fB\-pathspecs\fR "on"|"off"
 Control parameter interpretation with xorriso actions -add and -path_list.

test/xorriso.c

@@ -3630,7 +3630,8 @@ int Xorriso_status(struct XorrisO *xorriso, char *filter, FILE *fp, int flag)
    Xorriso_status_result(xorriso,filter,fp,flag&2);
 
  is_default= (xorriso->do_follow_pattern && (!xorriso->do_follow_param)
-              && xorriso->do_follow_mount && !xorriso->do_follow_links);
+              && xorriso->do_follow_mount && (!xorriso->do_follow_links)
+              && xorriso->follow_link_limit==100);
  mode[0]= 0;
  if(xorriso->do_follow_pattern)
    strcat(mode,":pattern");
@@ -3642,6 +3643,7 @@ int Xorriso_status(struct XorrisO *xorriso, char *filter, FILE *fp, int flag)
    strcat(mode,":mount");
  if(mode[0]==0)
    strcpy(mode, ":off");
+ sprintf(mode+strlen(mode), ":limit=%d", xorriso->follow_link_limit);
  sprintf(line,"-follow %s\n", mode+1);
  if(!(is_default && no_defaults))
    Xorriso_status_result(xorriso,filter,fp,flag&2);
@@ -5865,6 +5867,7 @@ int Xorriso_option_iso_rr_pattern(struct XorrisO *xorriso, char *mode,int flag)
 int Xorriso_option_follow(struct XorrisO *xorriso, char *mode, int flag)
 {
  int was_fl, was_fm, was_fpr, was_fpt, l;
+ double num;
  char *cpt, *npt;
 
  was_fpt= xorriso->do_follow_pattern;
@@ -5899,6 +5902,7 @@ int Xorriso_option_follow(struct XorrisO *xorriso, char *mode, int flag)
      xorriso->do_follow_param= 0;
      xorriso->do_follow_links= 0;
      xorriso->do_follow_mount= 1;
+     xorriso->follow_link_limit= 100;
    } else if(strncmp(cpt, "link", l)==0 || strncmp(cpt,"links", l)==0) {
      xorriso->do_follow_links= 1;
    } else if(strncmp(cpt, "mount", l)==0) {
@@ -5907,12 +5911,21 @@ int Xorriso_option_follow(struct XorrisO *xorriso, char *mode, int flag)
      xorriso->do_follow_param= 1;
    } else if(strncmp(cpt, "pattern", l)==0) {
      xorriso->do_follow_pattern= 1;
+   } else if(strncmp(cpt, "limit=", 6)==0) {
+     sscanf(cpt+6, "%lf", &num);
+     if(num<=0 || num>1.0e6) {
+       sprintf(xorriso->info_text, "-follow: Value too %s with '%s'",
+               num<=0 ? "small" : "large", cpt+6);
+       goto sorry_ex;
+     }
+     xorriso->follow_link_limit= num;
    } else {
 unknown_mode:;
      if(l<SfileadrL)
        sprintf(xorriso->info_text, "-follow: unknown mode '%s'", cpt);
      else
        sprintf(xorriso->info_text, "-follow: oversized mode parameter (%d)",l);
+sorry_ex:
      Xorriso_msgs_submit(xorriso, 0, xorriso->info_text, 0, "SORRY", 0);
      xorriso->do_follow_pattern= was_fpt;
      xorriso->do_follow_param= was_fpr;
@@ -6084,7 +6097,7 @@ int Xorriso_option_help(struct XorrisO *xorriso, int flag)
 "                 Delete empty directories.",
 "  --             Mark end of particular action argument list.",
 "",
-"  -follow \"on\"|\"pattern:param:link:mount\"|\"default\"|\"off\"",
+"  -follow \"on\"|\"pattern:param:link:mount:limit=#\"|\"default\"|\"off\"",
 "                 Follow symbolic links and mount points within disk_path.",
 "",
 "  -overwrite \"on\"|\"nondir\"|\"off\"",

test/xorriso_timestamp.h

@@ -1 +1 @@
-#define Xorriso_timestamP "2007.12.15.183022"
+#define Xorriso_timestamP "2007.12.16.103456"