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, 49 insertions, 0 deletions

diff --git a/include/osmocom/netif/channel.h b/include/osmocom/netif/channel.h
new file mode 100644
index 0000000..65955e8
--- /dev/null
+++ b/include/osmocom/netif/channel.h
@@ -0,0 +1,49 @@
+#ifndef _CHANNEL_H_
+#define _CHANNEL_H_
+
+#include <stdint.h>
+
+#define CHAN_SIGN_OML	0
+#define CHAN_SIGN_RSL	1
+
+enum {
+	CHAN_NONE,
+	CHAN_ABIS_IPA_SERVER,
+	CHAN_MAX,
+};
+
+#define CHAN_F_DEFAULT		(1 << 0)
+#define CHAN_F_BUFFERED		(1 << 1)
+#define CHAN_F_STREAM		(1 << 2)
+#define CHAN_F_ERRORS		(1 << 3)
+#define CHAN_F_MAX		(1 << 4)
+
+struct osmo_chan;
+struct msgb;
+
+struct osmo_chan_type {
+	int	type;
+	int	datasiz;
+
+	int	(*create)(struct osmo_chan *chan);
+	void	(*destroy)(struct osmo_chan *chan);
+	int	(*open)(struct osmo_chan *chan);
+	void	(*close)(struct osmo_chan *chan);
+	int	(*enqueue)(struct osmo_chan *chan, struct msgb *msg);
+};
+
+struct osmo_chan {
+	void			*ctx;
+	struct osmo_chan_type	*ops;
+	char			data[0];
+};
+
+struct osmo_chan *osmo_chan_create(void *ctx, int type);
+void osmo_chan_destroy(struct osmo_chan *c);
+
+int osmo_chan_open(struct osmo_chan *c);
+void osmo_chan_close(struct osmo_chan *c);
+
+int osmo_chan_enqueue(struct osmo_chan *c, struct msgb *msg);
+
+#endif /* _CHANNEL_H_ */