sd-bus: introduce new match type "arg0has=" for matching arrays of strings

Previously, sd-bus inofficially already supported bus matches that
tested a string against an array of strings ("as"). This was done via an
enhanced way to interpret "arg0=" matches. This is problematic however,
since clients have no way to determine if their respective
implementation understood strv matches or not, thus allowing invalid
matches to be installed without a way to detect that.

This patch changes the logic to only allow such matches with a new
"arg0has=" syntax. This has the benefit that non-conforming
implementations will return a parse error and a client application may
thus efficiently detect support for the match type.

Matches of this type are useful for "udev"-like systems that "tag" objects
with a number of strings, and clients need to be able to match against
any of these "tags".

The name "has" takes inspiration from Python's ".has_key()" construct.

1 files changed, 22 insertions, 1 deletions

diff --git a/src/libsystemd/sd-bus/bus-kernel.c b/src/libsystemd/sd-bus/bus-kernel.c
index 21f3700128..a217cf1a23 100644
--- a/src/libsystemd/sd-bus/bus-kernel.c
+++ b/src/libsystemd/sd-bus/bus-kernel.c
@@ -167,6 +167,27 @@ static void add_bloom_arg(void *data, size_t size, unsigned n_hash, unsigned i,
         bloom_add_prefixes(data, size, n_hash, buf, t, '/');
 }
 
+static void add_bloom_arg_has(void *data, size_t size, unsigned n_hash, unsigned i, const char *t) {
+        char buf[sizeof("arg")-1 + 2 + sizeof("has")];
+        char *e;
+
+        assert(data);
+        assert(size > 0);
+        assert(i < 64);
+        assert(t);
+
+        e = stpcpy(buf, "arg");
+        if (i < 10)
+                *(e++) = '0' + (char) i;
+        else {
+                *(e++) = '0' + (char) (i / 10);
+                *(e++) = '0' + (char) (i % 10);
+        }
+
+        strcpy(e, "has");
+        bloom_add_pair(data, size, n_hash, buf, t);
+}
+
 static int bus_message_setup_bloom(sd_bus_message *m, struct kdbus_bloom_filter *bloom) {
         void *data;
         unsigned i;
@@ -221,7 +242,7 @@ static int bus_message_setup_bloom(sd_bus_message *m, struct kdbus_bloom_filter
                                 return r;
 
                         while ((r = sd_bus_message_read_basic(m, contents[0], &t)) > 0)
-                                add_bloom_arg(data, m->bus->bloom_size, m->bus->bloom_n_hash, i, t);
+                                add_bloom_arg_has(data, m->bus->bloom_size, m->bus->bloom_n_hash, i, t);
                         if (r < 0)
                                 return r;