Debug pretrigger capture facility

9 files changed, 174 insertions, 35 deletions

diff --git a/src/src/acl.c b/src/src/acl.c
index 19c1bbbd9..fa1172331 100644
--- a/src/src/acl.c
+++ b/src/src/acl.c
@@ -3498,25 +3498,39 @@ for (; cb; cb = cb->next)
 	      }
 	    else if (Ustrncmp(pp, "kill", 4) == 0)
 	      {
-	      for (pp += 4; *pp && *pp != '/';) pp++;
+	      pp += 4;
 	      kill = TRUE;
 	      }
 	    else if (Ustrncmp(pp, "stop", 4) == 0)
 	      {
-	      for (pp += 4; *pp && *pp != '/';) pp++;
+	      pp += 4;
 	      stop = TRUE;
 	      }
-	    else
-	      while (*pp && *pp != '/') pp++;
+	    else if (Ustrncmp(pp, "pretrigger=", 11) == 0)
+		debug_pretrigger_setup(pp+11);
+	    else if (Ustrncmp(pp, "trigger=", 8) == 0)
+	      {
+	      if (Ustrncmp(pp += 8, "now", 3) == 0)
+		{
+		pp += 3;
+		debug_trigger_fire();
+		}
+	      else if (Ustrncmp(pp, "paniclog", 8) == 0)
+		{
+		pp += 8;
+		dtrigger_selector |= BIT(DTi_panictrigger);
+		}
+	      }
+	    while (*pp && *pp != '/') pp++;
 	    p = pp;
 	    }
 
-	    if (kill)
-	      debug_logging_stop(TRUE);
-	    else if (stop)
-	      debug_logging_stop(FALSE);
-	    else
-	      debug_logging_activate(debug_tag, debug_opts);
+	  if (kill)
+	    debug_logging_stop(TRUE);
+	  else if (stop)
+	    debug_logging_stop(FALSE);
+	  else if (debug_tag || debug_opts)
+	    debug_logging_activate(debug_tag, debug_opts);
 	  break;
 	  }
 
diff --git a/src/src/child.c b/src/src/child.c
index 4a262d623..07115bee4 100644
--- a/src/src/child.c
+++ b/src/src/child.c
@@ -76,7 +76,7 @@ int n = 0;
 int extra = pcount ? *pcount : 0;
 uschar **argv;
 
-argv = store_get((extra + acount + MAX_CLMACROS + 21) * sizeof(char *), FALSE);
+argv = store_get((extra + acount + MAX_CLMACROS + 24) * sizeof(char *), FALSE);
 
 /* In all case, the list starts out with the path, any macros, and a changed
 config file. */
@@ -88,10 +88,7 @@ if (clmacro_count > 0)
   n += clmacro_count;
   }
 if (f.config_changed)
-  {
-  argv[n++] = US"-C";
-  argv[n++] = config_main_filename;
-  }
+  { argv[n++] = US"-C"; argv[n++] = config_main_filename; }
 
 /* These values are added only for non-minimal cases. If debug_selector is
 precisely D_v, we have to assume this was started by a non-admin user, and
@@ -120,22 +117,23 @@ if (!minimal)
 	}
       }
     }
+  if (debug_pretrigger_buf)
+    { argv[n++] = US"-dp"; argv[n++] = string_sprintf("0x%x", debug_pretrigger_bsize); }
+  if (dtrigger_selector != 0)
+    argv[n++] = string_sprintf("-dt=0x%x", dtrigger_selector);
   DEBUG(D_any)
     {
     argv[n++] = US"-MCd";
     argv[n++] = US process_purpose;
     }
-  if (!f.testsuite_delays) argv[n++] = US"-odd";
-  if (f.dont_deliver) argv[n++] = US"-N";
-  if (f.queue_smtp) argv[n++] = US"-odqs";
-  if (f.synchronous_delivery) argv[n++] = US"-odi";
+  if (!f.testsuite_delays)	argv[n++] = US"-odd";
+  if (f.dont_deliver)		argv[n++] = US"-N";
+  if (f.queue_smtp)		argv[n++] = US"-odqs";
+  if (f.synchronous_delivery)	argv[n++] = US"-odi";
   if (connection_max_messages >= 0)
     argv[n++] = string_sprintf("-oB%d", connection_max_messages);
   if (*queue_name)
-    {
-    argv[n++] = US"-MCG";
-    argv[n++] = queue_name;
-    }
+    { argv[n++] = US"-MCG"; argv[n++] = queue_name; }
   }
 
 /* Now add in any others that are in the call. Remember which they were,
diff --git a/src/src/debug.c b/src/src/debug.c
index 92cad6d48..7b9be057b 100644
--- a/src/src/debug.c
+++ b/src/src/debug.c
@@ -13,6 +13,8 @@ static uschar  debug_buffer[2048];
 static uschar *debug_ptr = debug_buffer;
 static int     debug_prefix_length = 0;
 
+static unsigned pretrigger_writeoff;
+static unsigned pretrigger_readoff;
 
 
 const uschar * rc_names[] = {		/* Mostly for debug output */
@@ -318,8 +320,40 @@ if (debug_ptr[-1] == '\n')
       }
     }
 
-  fprintf(debug_file, "%s", CS debug_buffer);
-  fflush(debug_file);
+  if (debug_pretrigger_buf)
+    {
+    int needed = Ustrlen(debug_buffer), avail;
+    char c;
+
+    if (needed > debug_pretrigger_bsize)
+      needed = debug_pretrigger_bsize;
+    if ((avail = pretrigger_readoff - pretrigger_writeoff) <= 0)
+      avail += debug_pretrigger_bsize;
+
+    /* We have a pretrigger set up, trigger not yet hit. Copy the line(s) to the
+    pretrig buffer, dropping earlier lines if needed but truncating this line if
+    the pbuf is maxed out.  In the PTB the lines are NOT nul-terminated. */
+
+    while (avail < needed)
+      do
+	{
+	avail++;
+        c = debug_pretrigger_buf[pretrigger_readoff];
+	if (++pretrigger_readoff >= debug_pretrigger_bsize) pretrigger_readoff = 0;
+	}
+      while (c && c != '\n' && pretrigger_readoff != pretrigger_writeoff);
+
+    for (int i = 0; needed; i++, needed--)
+      {
+      debug_pretrigger_buf[pretrigger_writeoff] = debug_buffer[i];
+      if (++pretrigger_writeoff >= debug_pretrigger_bsize) pretrigger_writeoff = 0;
+      }
+    }
+  else
+    {
+    fprintf(debug_file, "%s", CS debug_buffer);
+    fflush(debug_file);
+    }
   debug_ptr = debug_buffer;
   debug_prefix_length = 0;
   }
@@ -410,4 +444,54 @@ else
 }
 
 
+/**************************************************************/
+/* Pretrigger handling for debug.  The debug_printf implementation
+diverts output to a circular buffer if the buffer is set up.
+The routines here set up the buffer, and unload it to file (and release it).
+What ends up in the buffer is subject to the usual debug_selector. */
+
+void
+debug_pretrigger_setup(const uschar * size_string)
+{
+long size = Ustrtol(size_string, NULL, 0);
+if (size > 0)
+  {
+  unsigned bufsize = MIN(size, 16384);
+
+  dtrigger_selector |= BIT(DTi_pretrigger);
+  if (debug_pretrigger_buf) store_free(debug_pretrigger_buf);
+  debug_pretrigger_buf = store_malloc((size_t)(debug_pretrigger_bsize = bufsize));
+  pretrigger_readoff = pretrigger_writeoff = 0;
+  }
+}
+
+void
+debug_trigger_fire(void)
+{
+int nbytes;
+
+if (!debug_pretrigger_buf) return;
+
+if (debug_file && (nbytes = pretrigger_writeoff - pretrigger_readoff) != 0)
+  if (nbytes > 0)
+    fwrite(debug_pretrigger_buf + pretrigger_readoff, 1, nbytes, debug_file);
+  else
+    {
+    fwrite(debug_pretrigger_buf + pretrigger_readoff, 1,
+      debug_pretrigger_bsize - pretrigger_readoff, debug_file);
+    fwrite(debug_pretrigger_buf, 1, pretrigger_writeoff, debug_file);
+    }
+
+debug_pretrigger_discard();
+}
+
+void
+debug_pretrigger_discard(void)
+{
+if (debug_pretrigger_buf) store_free(debug_pretrigger_buf);
+debug_pretrigger_buf = NULL;
+dtrigger_selector = 0;
+}
+
+
 /* End of debug.c */
diff --git a/src/src/exim.c b/src/src/exim.c
index 664d5d7f1..b59157286 100644
--- a/src/src/exim.c
+++ b/src/src/exim.c
@@ -2655,21 +2655,36 @@ on the second character (the one after '-'), to save some effort. */
     #endif
     break;
 
-    /* -d: Set debug level (see also -v below) or set the drop_cr option.
-    The latter is now a no-op, retained for compatibility only. If -dd is used,
-    debugging subprocesses of the daemon is disabled. */
-
     case 'd':
+
+    /* -dropcr: Set this option.  Now a no-op, retained for compatibility only. */
+
     if (Ustrcmp(argrest, "ropcr") == 0)
       {
       /* drop_cr = TRUE; */
       }
 
-    /* Use an intermediate variable so that we don't set debugging while
-    decoding the debugging bits. */
+    /* -dp: Set up a debug pretrigger buffer with given size. */
+
+    else if (Ustrcmp(argrest, "p") == 0)
+      if (++i >= argc)
+	badarg = TRUE;
+      else
+	debug_pretrigger_setup(argv[i]);
+
+    /* -dt: Set a debug trigger selector */
+
+    else if (Ustrncmp(argrest, "t=", 2) == 0)
+      dtrigger_selector = (unsigned int) Ustrtol(argrest + 2, NULL, 0);
+
+    /* -d: Set debug level (see also -v below).
+    If -dd is used, debugging subprocesses of the daemon is disabled. */
 
     else
       {
+      /* Use an intermediate variable so that we don't set debugging while
+      decoding the debugging bits. */
+
       unsigned int selector = D_default;
       debug_selector = 0;
       debug_file = NULL;
diff --git a/src/src/functions.h b/src/src/functions.h
index d27c23baa..4b4ff5e14 100644
--- a/src/src/functions.h
+++ b/src/src/functions.h
@@ -193,7 +193,10 @@ extern void    debug_printf_indent(const char *, ...) PRINTF_FUNCTION(1,2);
 extern void    debug_print_string(uschar *);
 extern void    debug_print_tree(const char *, tree_node *);
 extern void    debug_vprintf(int, const char *, va_list);
+extern void    debug_pretrigger_setup(const uschar *);
+extern void    debug_pretrigger_discard(void);
 extern void    debug_print_socket(int);
+extern void    debug_trigger_fire(void);
 
 extern void    decode_bits(unsigned int *, size_t, int *,
 	           uschar *, bit_table *, int, uschar *, int);
diff --git a/src/src/globals.c b/src/src/globals.c
index 7f7ceac00..7e50867b2 100644
--- a/src/src/globals.c
+++ b/src/src/globals.c
@@ -815,8 +815,10 @@ bit_table debug_options[]      = { /* must be in alphabetical order and use
   BIT_TABLE(D, verify),
 };
 int     debug_options_count    = nelem(debug_options);
-
+unsigned debug_pretrigger_bsize= 0;
+uschar * debug_pretrigger_buf  = NULL;
 unsigned int debug_selector    = 0;
+
 int     delay_warning[DELAY_WARNING_SIZE] = { DELAY_WARNING_SIZE, 1, 24*60*60 };
 uschar *delay_warning_condition=
   US"${if or {"
@@ -897,6 +899,7 @@ uschar *dnslist_value          = NULL;
 tree_node *domainlist_anchor   = NULL;
 int     domainlist_count       = 0;
 uschar *dsn_from               = US DEFAULT_DSN_FROM;
+unsigned int dtrigger_selector = 0;
 
 int     errno_quota            = ERRNO_QUOTA;
 uschar *errors_copy            = NULL;
diff --git a/src/src/globals.h b/src/src/globals.h
index 10dd3effc..de4670a81 100644
--- a/src/src/globals.h
+++ b/src/src/globals.h
@@ -487,6 +487,8 @@ extern FILE   *debug_file;             /* Where to write debugging info */
 extern int     debug_notall[];         /* Debug options excluded from +all */
 extern bit_table debug_options[];      /* Table of debug options */
 extern int     debug_options_count;    /* Size of table */
+extern unsigned debug_pretrigger_bsize;
+extern uschar *debug_pretrigger_buf;   /* circular buffer for precapture */
 extern BOOL    debug_store;	       /* Do extra checks on store_reset */
 extern int     delay_warning[];        /* Times between warnings */
 extern uschar *delay_warning_condition; /* Condition string for warnings */
@@ -576,6 +578,8 @@ extern int     domainlist_count;       /* Number defined */
 /* This option is now a no-opt, retained for compatibility */
 extern BOOL    drop_cr;                /* For broken local MUAs */
 
+extern unsigned int dtrigger_selector; /* when to start debug */
+
 extern uschar *dsn_from;               /* From: string for DSNs */
 
 extern BOOL    envelope_to_remove;     /* Remove envelope_to_headers */
diff --git a/src/src/log.c b/src/src/log.c
index fe9bd0c9f..8bdb244bd 100644
--- a/src/src/log.c
+++ b/src/src/log.c
@@ -905,6 +905,11 @@ if (!path_inspected)
       "More than one path given in log_file_path: using %s", file_path);
   }
 
+/* Optionally trigger debug */
+
+if (flags & LOG_PANIC && dtrigger_selector & BIT(DTi_panictrigger))
+  debug_trigger_fire();
+
 /* If debugging, show all log entries, but don't show headers. Do it all
 in one go so that it doesn't get split when multi-processing. */
 
@@ -1470,7 +1475,11 @@ misconfiguration.
 
 The first use of this is in ACL logic, "control = debug/tag=foo/opts=+expand"
 which can be combined with conditions, etc, to activate extra logging only
-for certain sources. The second use is inetd wait mode debug preservation. */
+for certain sources. The second use is inetd wait mode debug preservation.
+
+It might be nice, in ACL-initiated pretrigger mode, to not create the file
+immediately but only upon a trigger - but we'd need another cmdline option
+to pass the name through child_exxec_exim(). */
 
 void
 debug_logging_activate(uschar *tag_name, uschar *opts)
@@ -1482,7 +1491,7 @@ if (debug_file)
   return;
   }
 
-if (tag_name != NULL && (Ustrchr(tag_name, '/') != NULL))
+if (tag_name && (Ustrchr(tag_name, '/') != NULL))
   {
   log_write(0, LOG_MAIN|LOG_PANIC, "debug tag may not contain a '/' in: %s",
       tag_name);
@@ -1512,11 +1521,13 @@ else
 void
 debug_logging_stop(BOOL kill)
 {
+debug_pretrigger_discard();
 if (!debug_file || !debuglog_name[0]) return;
 
 debug_selector = 0;
 fclose(debug_file);
 debug_file = NULL;
+debug_fd = -1;
 if (kill) unlink_log(lt_debug);
 }
 
diff --git a/src/src/macros.h b/src/src/macros.h
index 80e0ecbe1..5e26a7bce 100644
--- a/src/src/macros.h
+++ b/src/src/macros.h
@@ -106,7 +106,7 @@ don't make the file descriptors two-way. */
 /* Debugging control */
 
 #define DEBUG(x)      if (debug_selector & (x))
-#define HDEBUG(x)     if (host_checking || (debug_selector & (x)))
+#define HDEBUG(x)     if (host_checking || debug_selector & (x))
 
 /* The default From: text for DSNs */
 
@@ -422,6 +422,13 @@ enum {
                                          D_timestamp   | \
                                          D_resolver))
 
+/* Bits for debug triggers */
+
+enum {
+  DTi_panictrigger,
+  DTi_pretrigger,
+};
+
 /* Options bits for logging. Those that have values < BITWORDSIZE can be used
 in calls to log_write(). The others are put into later words in log_selector
 and are only ever tested independently, so they do not need bit mask