ifupdown: support "source-directory" stanza

Support the "source-directory" stanza from ifupdown[1]. source-directory
will include all files in the named directory. Similar to the Busybox
version of the "source" stanza, this version of source-directory does
not currently support shell wildcards.

We only check that the stanza starts with "source-dir" as ifupdown does[2].

[1] https://manpages.debian.org/stretch/ifupdown/interfaces.5.en.html#INCLUDING_OTHER_FILES
[2] https://salsa.debian.org/debian/ifupdown/blob/0.8.33/config.c#L498

function                                             old     new   delta
read_interfaces                                     1150    1241     +91

Signed-off-by: Brandon Maier <brandon.maier@rockwellcollins.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 16 insertions, 0 deletions

diff --git a/networking/ifupdown.c b/networking/ifupdown.c
index 5481134e5..80fce87a6 100644
--- a/networking/ifupdown.c
+++ b/networking/ifupdown.c
@@ -1022,6 +1022,22 @@ static struct interfaces_file_t *read_interfaces(const char *filename, struct in
                         currently_processing = NONE;
                 } else if (strcmp(first_word, "source") == 0) {
                         read_interfaces(next_word(&rest_of_line), defn);
+                } else if (is_prefixed_with(first_word, "source-dir")) {
+                        const char *dirpath;
+                        DIR *dir;
+                        struct dirent *entry;
+
+                        dirpath = next_word(&rest_of_line);
+                        dir = xopendir(dirpath);
+                        while ((entry = readdir(dir)) != NULL) {
+                                char *path;
+                                if (entry->d_name[0] == '.')
+                                        continue;
+                                path = concat_path_file(dirpath, entry->d_name);
+                                read_interfaces(path, defn);
+                                free(path);
+                        }
+                        closedir(dir);
                 } else {
                         switch (currently_processing) {
                         case IFACE: