DEV: haring: add a new option "-r" to automatically repair broken files

In case a file-backed ring was not properly synced before being dumped,
the output can look bogus due to the head pointer not being perfectly
up to date. In this case, passing "-r" will make haring automatically
skip entries not starting with a zero, and resynchronize with the rest
of the messages.

This should be backported to 2.6.

diff --git a/dev/haring/haring.c b/dev/haring/haring.c
index 27e03eecfa2b994cd52101c8c0a8cdb8710bc84c..53352cbd165cbea4e9d0c9ede7f68ea965f2834d 100644 (file)
--- a/dev/haring/haring.c
+++ b/dev/haring/haring.c
@@ -37,6 +37,7 @@
 
 int force = 0; // force access to a different layout
 int lfremap = 0; // remap LF in traces
+int repair = 0; // repair file
 
 
 /* display the message and exit with the code */
@@ -61,6 +62,7 @@ __attribute__((noreturn)) void usage(int code, const char *arg0)
            "options :\n"
            "  -f           : force accessing a non-matching layout for 'ring struct'\n"
            "  -l           : replace LF in contents with CR VT\n"
+           "  -r           : \"repair\" corrupted file (actively search for message boundaries)\n"
            "\n"
            "", arg0);
 }
@@ -146,6 +148,14 @@ int dump_ring(struct ring *ring, size_t ofs, int flags)
                 * stop before the end.
                 */
                while (ofs + 1 < b_data(&buf)) {
+                       if (unlikely(repair && *b_peek(&buf, ofs))) {
+                               /* in repair mode we consider that we could have landed
+                                * in the middle of a message so we skip all bytes till
+                                * the next zero.
+                                */
+                               ofs++;
+                               continue;
+                       }
                        cnt = 1;
                        len = b_peek_varint(&buf, ofs + cnt, &msg_len);
                        if (!len)
@@ -219,6 +229,8 @@ int main(int argc, char **argv)
                        force = 1;
                else if (strcmp(argv[0], "-l") == 0)
                        lfremap = 1;
+               else if (strcmp(argv[0], "-r") == 0)
+                       repair = 1;
                else if (strcmp(argv[0], "--") == 0)
                        break;
                else