ipa: initial addition of helper functions and examples

This patch adds IPA helper function that can be use on top of stream
sockets.

The current API is just a copy and paste from libosmo-abis, it will
change in follow up patches to improve it.

1 files changed, 73 insertions, 0 deletions

diff --git a/src/ipa.c b/src/ipa.c
new file mode 100644
index 0000000..335c830
--- /dev/null
+++ b/src/ipa.c
@@ -0,0 +1,73 @@
+#include <stdlib.h>
+#include <arpa/inet.h>
+#include <errno.h>
+
+#include <osmocom/core/logging.h>
+#include <osmocom/core/msgb.h>
+#include <osmocom/netif/ipa.h>
+
+#define IPA_ALLOC_SIZE 1200
+
+struct msgb *osmo_ipa_msg_alloc(int headroom)
+{
+	struct msgb *msg;
+
+	headroom += sizeof(struct ipa_head);
+
+	msg = msgb_alloc_headroom(IPA_ALLOC_SIZE + headroom, headroom, "IPA");
+	if (msg == NULL) {
+		LOGP(DLINP, LOGL_ERROR, "cannot allocate message\n");
+		return NULL;
+	}
+	return msg;
+}
+
+void osmo_ipa_msg_push_header(struct msgb *msg, uint8_t proto)
+{
+	struct ipa_head *hh;
+
+	msg->l2h = msg->data;
+	hh = (struct ipa_head *) msgb_push(msg, sizeof(*hh));
+	hh->proto = proto;
+	hh->len = htons(msgb_l2len(msg));
+}
+
+int osmo_ipa_msg_recv(int fd, struct msgb *msg)
+{
+	struct ipa_head *hh;
+	int len, ret;
+
+	/* first read our 3-byte header */
+	hh = (struct ipa_head *) msg->data;
+	ret = recv(fd, msg->data, sizeof(*hh), 0);
+	if (ret <= 0) {
+		return ret;
+	} else if (ret != sizeof(*hh)) {
+		LOGP(DLINP, LOGL_ERROR, "too small message received\n");
+		return -EIO;
+	}
+	msgb_put(msg, ret);
+
+	/* then read the length as specified in header */
+	msg->l2h = msg->data + sizeof(*hh);
+	len = ntohs(hh->len);
+
+	if (len < 0 || IPA_ALLOC_SIZE < len + sizeof(*hh)) {
+		LOGP(DLINP, LOGL_ERROR, "bad message length of %d bytes, "
+					"received %d bytes\n", len, ret);
+		msgb_free(msg);
+		return -EIO;
+	}
+
+	ret = recv(fd, msg->l2h, len, 0);
+	if (ret <= 0) {
+		msgb_free(msg);
+		return ret;
+	} else if (ret < len) {
+		LOGP(DLINP, LOGL_ERROR, "trunked message received\n");
+		msgb_free(msg);
+		return -EIO;
+	}
+	msgb_put(msg, ret);
+	return ret;
+}