[OpenWrt-Devel] [PATCH v2] ubus: use network order in ubus message header fields

[Eyal Birger]

Changing the ubus message header fields from 'host' order to 'network' order
allows passing ubus messages between hosts with different endianity.

Example use (creating a ubus proxy):

on host A (e.g. big endian router already running ubusd), run:
$ socat TCP-LISTEN:5699,fork UNIX:/var/run/ubus.sock &

On host B (e.g. little endian development PC) run:
$ socat UNIX-LISTEN:/var/run/ubus.sock,fork TCP:<host A IP>:5699 &

Now ubus applications can be run on host B and seamlessly interact with ubus
applications on host A.

Signed-off-by: Eyal Birger <eyal.birger at gmail.com>

----
v2:
	Applied change to ubusd too. Thanks Felix!
---
 libubus-io.c |  7 +++++--
 ubusd.c      | 14 ++++++++++++--
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/libubus-io.c b/libubus-io.c
index b9b3128..9320bf3 100644
--- a/libubus-io.c
+++ b/libubus-io.c
@@ -133,8 +133,8 @@ int __hidden ubus_send_msg(struct ubus_context *ctx, uint32_t seq,
 
 	hdr.version = 0;
 	hdr.type = cmd;
-	hdr.seq = seq;
-	hdr.peer = peer;
+	hdr.seq = cpu_to_be16(seq);
+	hdr.peer = cpu_to_be32(peer);
 
 	if (!msg) {
 		blob_buf_init(&b, 0);
@@ -281,6 +281,9 @@ static bool get_next_msg(struct ubus_context *ctx, int *recv_fd)
 		return false;
 	}
 
+	hdrbuf.hdr.seq = be16_to_cpu(hdrbuf.hdr.seq);
+	hdrbuf.hdr.peer = be32_to_cpu(hdrbuf.hdr.peer);
+
 	if (!ubus_validate_hdr(&hdrbuf.hdr))
 		return false;
 
diff --git a/ubusd.c b/ubusd.c
index f1f8ac7..7279a70 100644
--- a/ubusd.c
+++ b/ubusd.c
@@ -110,8 +110,15 @@ static int ubus_msg_writev(int fd, struct ubus_msg_buf *ub, int offset)
 	}
 
 	if (offset < sizeof(ub->hdr)) {
-		iov[0].iov_base = ((char *) &ub->hdr) + offset;
-		iov[0].iov_len = sizeof(ub->hdr) - offset;
+		struct ubus_msghdr hdr;
+
+		hdr.version = ub->hdr.version;
+		hdr.type = ub->hdr.type;
+		hdr.seq = cpu_to_be16(ub->hdr.seq);
+		hdr.peer = cpu_to_be32(ub->hdr.peer);
+
+		iov[0].iov_base = ((char *) &hdr) + offset;
+		iov[0].iov_len = sizeof(hdr) - offset;
 		iov[1].iov_base = (char *) ub->data;
 		iov[1].iov_len = ub->len;
 
@@ -275,6 +282,9 @@ retry:
 		if (!cl->pending_msg)
 			goto disconnect;
 
+		cl->hdrbuf.hdr.seq = be16_to_cpu(cl->hdrbuf.hdr.seq);
+		cl->hdrbuf.hdr.peer = be32_to_cpu(cl->hdrbuf.hdr.peer);
+
 		memcpy(&cl->pending_msg->hdr, &cl->hdrbuf.hdr, sizeof(cl->hdrbuf.hdr));
 		memcpy(cl->pending_msg->data, &cl->hdrbuf.data, sizeof(cl->hdrbuf.data));
 	}
-- 
2.4.0
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