Quoting Christian Brauner (christianvanbrau...@gmail.com):
> This functions updates absolute paths for overlay upper- and workdirs so users
> can simply clone and start new containers without worrying about absolute
> paths
> in lxc.mount.entry overlay entries.
>
> Signed-off-by: Christian Brauner <christianvanbrau...@gmail.com>
> ---
> src/lxc/confile.c | 102
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> src/lxc/confile.h | 3 ++
> 2 files changed, 105 insertions(+)
>
> diff --git a/src/lxc/confile.c b/src/lxc/confile.c
> index f7d6814..47b0b8b 100644
> --- a/src/lxc/confile.c
> +++ b/src/lxc/confile.c
> @@ -2598,6 +2598,108 @@ void clear_unexp_config_line(struct lxc_conf *conf,
> const char *key, bool rm_sub
> }
> }
>
> +bool clone_update_unexp_ovl_paths(struct lxc_conf *conf, const char *oldpath,
> + const char *newpath, const char *oldname,
> + const char *newname, const char *ovldir)
> +{
> + const char *key = "lxc.mount.entry";
> + int ret;
> + char *lstart = conf->unexpanded_config;
> + char *lend;
> + char *p;
> + char *q;
> + size_t newdirlen = strlen(ovldir) + strlen(newpath) + strlen(newname) +
> 2;
> + size_t olddirlen = strlen(ovldir) + strlen(oldpath) + strlen(oldname) +
> 2;
> + char *olddir = alloca(olddirlen + 1);
> + char *newdir = alloca(newdirlen + 1);
> +
> + ret = snprintf(olddir, olddirlen + 1, "%s=%s/%s", ovldir, oldpath,
> oldname);
> + if (ret < 0 || ret >= olddirlen + 1) {
> + ERROR("Bug in %s", __func__);
> + return false;
> + }
> + ret = snprintf(newdir, newdirlen + 1, "%s=%s/%s", ovldir, newpath,
> newname);
> + if (ret < 0 || ret >= newdirlen + 1) {
> + ERROR("Bug in %s", __func__);
> + return false;
> + }
> + if (!conf->unexpanded_config)
> + return true;
> + while (*lstart) {
> + lend = strchr(lstart, '\n');
> + if (!lend)
> + lend = lstart + strlen(lstart);
> + else
> + lend++;
> + if (strncmp(lstart, key, strlen(key)) != 0) {
> + lstart = lend;
> + continue;
> + }
> + p = strchr(lstart + strlen(key), '=');
> + if (!p) {
> + lstart = lend;
> + continue;
> + }
> + p++;
> + while (isblank(*p))
> + p++;
> + if (p >= lend)
> + continue;
> + /* Whenever an lxc.mount.entry entry is found in a line we
> check
> + * if the substring " overlay" or the substring " aufs" is
> + * present before doing any further work. We check for "
> + * overlay" and " aufs" since both substrings need to have at
> + * least one space before them in a valid overlay
> + * lxc.mount.entry (/A B overlay). When the space before is
> + * missing it is very likely that these substrings are part
> of a
> + * path or something else. */
> + if (!strstr(p, " overlay") && !strstr(p, " aufs")) {
> + lstart = lend;
> + continue;
> + }
> + if (!(q = strstr(p, olddir))) {
> + lstart = lend;
> + continue;
> + }
You're still not doing anything to ensure that 'overlays'/'aufs' and the
olddir are actually occurring on this same line. So they could be showing
up in a comment or just later line. Temporarily turning lend into '\0' is
the easiest way, but you could also do something like
if (!(q = strstr(p, " overlay")) && !(q=strstr(p, " aufs")))
goto next;
if (q >= lend)
goto next;
if (!(q = strstr(p, olddir)) || q >= lend)
goto next;
...
break;
next:
lstart = lend;
continue;
}
> +
> + /* replace the olddir with newdir */
> + if (olddirlen >= newdirlen) {
> + size_t diff = olddirlen - newdirlen;
> + memcpy(q, newdir, newdirlen);
> + if (olddirlen != newdirlen) {
> + memmove(q + newdirlen, q + newdirlen + diff,
> + strlen(q) - newdirlen - diff + 1);
> + lend -= diff;
> + conf->unexpanded_len -= diff;
> + }
> + lstart = lend;
> + } else {
> + char *new;
> + size_t diff = newdirlen - olddirlen;
> + size_t oldlen = conf->unexpanded_len;
> + size_t newlen = oldlen + diff;
> + size_t poffset = q - conf->unexpanded_config;
> + new = realloc(conf->unexpanded_config, newlen + 1);
> + if (!new) {
> + ERROR("Out of memory");
> + return false;
> + }
> + conf->unexpanded_len = newlen;
> + conf->unexpanded_alloced = newlen + 1;
> + new[newlen - 1] = '\0';
> + lend = new + (lend - conf->unexpanded_config);
> + /* move over the remainder to make room for the newdir
> */
> + memmove(new + poffset + newdirlen,
> + new + poffset + olddirlen,
> + oldlen - poffset - olddirlen + 1);
> + conf->unexpanded_config = new;
> + memcpy(new + poffset, newdir, newdirlen);
> + lstart = lend + diff;
> + }
> + }
> + return true;
> +}
> +
> bool clone_update_unexp_hooks(struct lxc_conf *conf, const char *oldpath,
> const char *newpath, const char *oldname, const char *newname)
> {
> diff --git a/src/lxc/confile.h b/src/lxc/confile.h
> index 8da3699..12ffd3c 100644
> --- a/src/lxc/confile.h
> +++ b/src/lxc/confile.h
> @@ -61,5 +61,8 @@ extern bool do_append_unexp_config_line(struct lxc_conf
> *conf, const char *key,
> extern void clear_unexp_config_line(struct lxc_conf *conf, const char *key,
> bool rm_subkeys);
> extern bool clone_update_unexp_hooks(struct lxc_conf *conf, const char
> *oldpath,
> const char *newpath, const char *oldname, const char *newmame);
> +bool clone_update_unexp_ovl_paths(struct lxc_conf *conf, const char *oldpath,
> + const char *newpath, const char *oldname,
> + const char *newname, const char *ovldir);
> extern bool network_new_hwaddrs(struct lxc_conf *conf);
> #endif
> --
> 2.6.2
>
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