src: add generic channel infrastructure and A-bis IPA server support

This patch adds the generic channel infrastructure that allows to
create channel of different types. Each channel has their own
configuration functions.

  struct osmo_chan *chan;
  chan = osmo_chan_create(tall_example, CHAN_ABIS_IPA_SERVER);
  ...

  /* specific configuration functions per supported channel. */
  osmo_chan_abis_ipa_server_set_cb_signalmsg(chan, signal_msg_cb);
  osmo_chan_abis_ipa_unit_add(chan, 1801, 0);

  /* open channel. */
  osmo_chan_open(chan);

The input path requires a callback to be registered. The output path
is handled through:

  int osmo_chan_enqueue(struct osmo_chan *c, struct msgb *msg);

The msg->dst must be set (it can be taken from the original message
to route one reply).

This patch also adds A-bis IPA server support. It has been tested with
e1inp_ipa_bsc_test available in libosmo-abis.

1 files changed, 52 insertions, 0 deletions

diff --git a/src/channel.c b/src/channel.c
new file mode 100644
index 0000000..5aedd83
--- /dev/null
+++ b/src/channel.c
@@ -0,0 +1,52 @@
+#include <osmocom/core/talloc.h>
+#include <osmocom/core/msgb.h>
+
+#include <osmocom/netif/channel.h>
+
+extern struct osmo_chan_type chan_abis_ipa_server;
+
+static struct osmo_chan_type *chan_type[CHAN_MAX] = {
+	[CHAN_ABIS_IPA_SERVER]	= &chan_abis_ipa_server,
+};
+
+struct osmo_chan *osmo_chan_create(void *ctx, int type_id)
+{
+	struct osmo_chan *c;
+
+	if (type_id >= CHAN_MAX)
+		return NULL;
+
+	c = talloc_zero_size(ctx, sizeof(struct osmo_chan) +
+			     chan_type[type_id]->datasiz);
+	if (c == NULL)
+		return NULL;
+
+	c->ops = chan_type[type_id];
+
+	if (c->ops->create(c) < 0) {
+		talloc_free(c);
+		return NULL;
+	}
+	return c;
+}
+
+void osmo_chan_destroy(struct osmo_chan *c)
+{
+	c->ops->destroy(c);
+	talloc_free(c);
+}
+
+int osmo_chan_open(struct osmo_chan *c)
+{
+	return c->ops->open(c);
+}
+
+void osmo_chan_close(struct osmo_chan *c)
+{
+	c->ops->close(c);
+}
+
+int osmo_chan_enqueue(struct osmo_chan *c, struct msgb *msg)
+{
+	return c->ops->enqueue(c, msg);
+}