6lowpan: modify udp compression/uncompression to match the standard

The previous code would just compress the UDP header and send the compressed
UDP header along with the uncompressed one.

Signed-off-by: Tony Cheneau <tony.cheneau@amnesiak.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 36 insertions, 3 deletions

diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
index 276971ba3ade..c9c3f3d18c41 100644
--- a/net/ieee802154/6lowpan.c
+++ b/net/ieee802154/6lowpan.c
@@ -284,6 +284,9 @@ lowpan_compress_udp_header(u8 **hc06_ptr, struct sk_buff *skb)
         /* checksum is always inline */
         memcpy(*hc06_ptr, &uh->check, 2);
         *hc06_ptr += 2;
+
+        /* skip the UDP header */
+        skb_pull(skb, sizeof(struct udphdr));
 }
 
 static inline int lowpan_fetch_skb_u8(struct sk_buff *skb, u8 *val)
@@ -309,9 +312,8 @@ static inline int lowpan_fetch_skb_u16(struct sk_buff *skb, u16 *val)
 }
 
 static int
-lowpan_uncompress_udp_header(struct sk_buff *skb)
+lowpan_uncompress_udp_header(struct sk_buff *skb, struct udphdr *uh)
 {
-        struct udphdr *uh = udp_hdr(skb);
         u8 tmp;
 
         if (!uh)
@@ -358,6 +360,14 @@ lowpan_uncompress_udp_header(struct sk_buff *skb)
                 /* copy checksum */
                 memcpy(&uh->check, &skb->data[0], 2);
                 skb_pull(skb, 2);
+
+                /*
+                 * UDP lenght needs to be infered from the lower layers
+                 * here, we obtain the hint from the remaining size of the
+                 * frame
+                 */
+                uh->len = htons(skb->len + sizeof(struct udphdr));
+                pr_debug("uncompressed UDP length: src = %d", uh->len);
         } else {
                 pr_debug("ERROR: unsupported NH format\n");
                 goto err;
@@ -944,8 +954,31 @@ lowpan_process_data(struct sk_buff *skb)
 
         /* UDP data uncompression */
         if (iphc0 & LOWPAN_IPHC_NH_C) {
-                if (lowpan_uncompress_udp_header(skb))
+                struct udphdr uh;
+                struct sk_buff *new;
+                if (lowpan_uncompress_udp_header(skb, &uh))
                         goto drop;
+
+                /*
+                 * replace the compressed UDP head by the uncompressed UDP
+                 * header
+                 */
+                new = skb_copy_expand(skb, sizeof(struct udphdr),
+                                      skb_tailroom(skb), GFP_ATOMIC);
+                kfree_skb(skb);
+
+                if (!new)
+                        return -ENOMEM;
+
+                skb = new;
+
+                skb_push(skb, sizeof(struct udphdr));
+                skb_reset_transport_header(skb);
+                skb_copy_to_linear_data(skb, &uh, sizeof(struct udphdr));
+
+                lowpan_raw_dump_table(__func__, "raw UDP header dump",
+                                      (u8 *)&uh, sizeof(uh));
+
                 hdr.nexthdr = UIP_PROTO_UDP;
         }