external: normalize file id lookup and warn on fallback reopen

Signed-off-by: Farzan Aman Khan <farzanaman99@gmail.com>

Author: cheese-cakee

Documentation/criu.txt

@@ -243,7 +243,8 @@ In other words, do not use it unless really needed.
     from the current mount namespace, which can not be dumped without using
     this option. The file is identified by 'mnt_id' (a field obtained from
     **/proc/**__pid__**/fdinfo/**__N__) and 'inode' (as returned by
-    *stat*(2)).
+    *stat*(2)). Both values can be provided either in decimal or in
+    hexadecimal (with or without a 0x prefix).
 
 *--external* **tty[**__rdev__**:**__dev__**]**::
     Dump an external TTY, identified by *st_rdev* and *st_dev* fields

criu/crtools.c

@@ -432,7 +432,7 @@ int main(int argc, char *argv[], char *envp[])
 	       "  --external RES        dump objects from this list as external resources:\n"
 	       "                        Formats of RES on dump:\n"
 	       "                            tty[rdev:dev]\n"
-	       "                            file[mnt_id:inode]\n"
+	       "                            file[mnt_id:inode] (mnt_id/inode: decimal or hex)\n"
 	       "                            dev[major/minor]:NAME\n"
 	       "                            unix[ino]\n"
 	       "                            mnt[MOUNTPOINT]:COOKIE\n"
@@ -505,7 +505,7 @@ int main(int argc, char *argv[], char *envp[])
 	       "                            tty[rdev:dev]\n"
 	       "                            pipe:[inode]\n"
 	       "                            socket:[inode]\n"
-	       "                            file[mnt_id:inode]\n"
+	       "                            file[mnt_id:inode] (mnt_id/inode: decimal or hex)\n"
 	       "                            /memfd:name\n"
 	       "                            path/to/file\n"
 	       "  --empty-ns net        Create a namespace, but don't restore its properties\n"

criu/external.c

@@ -1,3 +1,8 @@
+#include <errno.h>
+#include <limits.h>
+#include <stdint.h>
+#include <stdlib.h>
+
 #include "common/err.h"
 #include "common/list.h"
 #include "cr_options.h"
@@ -8,6 +13,60 @@
 
 #include "net.h"
 
+static bool parse_external_id_component(const char *id, char **end, unsigned long long *val)
+{
+	char *tmp;
+
+	errno = 0;
+	*val = strtoull(id, &tmp, 0);
+	if (!errno && tmp != id) {
+		*end = tmp;
+		return true;
+	}
+
+	/*
+	 * External regular file ids are emitted as hex without 0x prefix.
+	 * Accept such values for normalized matching as well.
+	 */
+	errno = 0;
+	*val = strtoull(id, &tmp, 16);
+	if (errno || tmp == id)
+		return false;
+
+	*end = tmp;
+	return true;
+}
+
+static bool parse_external_file_id(const char *id, unsigned int *mnt_id, uint64_t *inode)
+{
+	char *end = NULL;
+	unsigned long long val;
+
+	if (!strstartswith(id, "file["))
+		return false;
+	id += strlen("file[");
+
+	if (!parse_external_id_component(id, &end, &val))
+		return false;
+	if (val > UINT_MAX)
+		return false;
+	if (*end != ':')
+		return false;
+	*mnt_id = (unsigned int)val;
+
+	id = end + 1;
+	if (!parse_external_id_component(id, &end, &val))
+		return false;
+	if (*end != ']')
+		return false;
+	end++;
+	if (*end != '\0')
+		return false;
+
+	*inode = val;
+	return true;
+}
+
 int add_external(char *key)
 {
 	struct external *ext;
@@ -39,10 +98,18 @@ int add_external(char *key)
 bool external_lookup_id(char *id)
 {
 	struct external *ext;
+	unsigned int id_mnt_id, ext_mnt_id;
+	uint64_t id_inode, ext_inode;
+	bool normalized_id;
+
+	normalized_id = parse_external_file_id(id, &id_mnt_id, &id_inode);
 
 	list_for_each_entry(ext, &opts.external, node)
 		if (!strcmp(ext->id, id))
 			return true;
+		else if (normalized_id && parse_external_file_id(ext->id, &ext_mnt_id, &ext_inode) &&
+			 ext_mnt_id == id_mnt_id && ext_inode == id_inode)
+			return true;
 	return false;
 }
 

criu/files-reg.c

@@ -2216,6 +2216,9 @@ int open_path(struct file_desc *d, int (*open_cb)(int mntns_root, struct reg_fil
 			rfi->path = path;
 			goto ext;
 		}
+
+		pr_warn("No --inherit-fd mapping found for external file id %s, falling back to path-based reopen\n",
+			rfi->rfe->name);
 	}
 
 	if (rfi->remap) {