This patch drop the pre and postcount calculation from the
lowpan_uncompress_addr function.

We use instead a switch case over address_mode value, it's easier
to understand what's going on there.

Signed-off-by: Alexander Aring <alex.ar...@gmail.com>
---
 net/ieee802154/6lowpan.c | 151 +++++++++++++++++++++++++----------------------
 net/ieee802154/6lowpan.h |   8 ++-
 2 files changed, 87 insertions(+), 72 deletions(-)

diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c
index e9d6cbd..c711441 100644
--- a/net/ieee802154/6lowpan.c
+++ b/net/ieee802154/6lowpan.c
@@ -67,30 +67,6 @@ static const u8 lowpan_ttl_values[] = {0, 1, 64, 255};
 
 static LIST_HEAD(lowpan_devices);
 
-/*
- * Uncompression of linklocal:
- *   0 -> 16 bytes from packet
- *   1 -> 2  bytes from prefix - bunch of zeroes and 8 from packet
- *   2 -> 2  bytes from prefix - zeroes + 2 from packet
- *   3 -> 2  bytes from prefix - infer 8 bytes from lladdr
- *
- *  NOTE: => the uncompress function does change 0xf to 0x10
- *  NOTE: 0x00 => no-autoconfig => unspecified
- */
-static const u8 lowpan_unc_llconf[] = {0x0f, 0x28, 0x22, 0x20};
-
-/*
- * Uncompression of ctx-based:
- *   0 -> 0 bits  from packet [unspecified / reserved]
- *   1 -> 8 bytes from prefix - bunch of zeroes and 8 from packet
- *   2 -> 8 bytes from prefix - zeroes + 2 from packet
- *   3 -> 8 bytes from prefix - infer 8 bytes from lladdr
- */
-static const u8 lowpan_unc_ctxconf[] = {0x00, 0x88, 0x82, 0x80};
-
-/* Link local prefix */
-static const u8 lowpan_llprefix[] = {0xfe, 0x80};
-
 /* private device info */
 struct lowpan_dev_info {
        struct net_device       *real_dev; /* real WPAN device ptr */
@@ -182,50 +158,89 @@ lowpan_compress_addr_64(u8 **hc06_ptr, u8 shift, const 
struct in6_addr *ipaddr,
        return rol8(val, shift);
 }
 
-static void
-lowpan_uip_ds6_set_addr_iid(struct in6_addr *ipaddr, unsigned char *lladdr)
-{
-       memcpy(&ipaddr->s6_addr[8], lladdr, IEEE802154_ADDR_LEN);
-       /* second bit-flip (Universe/Local) is done according RFC2464 */
-       ipaddr->s6_addr[8] ^= 0x02;
-}
-
 /*
- * Uncompress addresses based on a prefix and a postfix with zeroes in
- * between. If the postfix is zero in length it will use the link address
- * to configure the IP address (autoconf style).
- * pref_post_count takes a byte where the first nibble specify prefix count
- * and the second postfix count (NOTE: 15/0xf => 16 bytes copy).
+ * Uncompress address function for source and
+ * destination address(non-multicast).
+ *
+ * address_mode is sam value or dam value.
  */
 static int
-lowpan_uncompress_addr(struct sk_buff *skb, struct in6_addr *ipaddr,
-       u8 const *prefix, u8 pref_post_count, unsigned char *lladdr)
+lowpan_uncompress_addr(struct sk_buff *skb,
+               struct in6_addr *ipaddr,
+               const u8 address_mode,
+               const struct ieee802154_addr *lladdr)
 {
-       u8 prefcount = pref_post_count >> 4;
-       u8 postcount = pref_post_count & 0x0f;
-
-       /* full nibble 15 => 16 */
-       prefcount = (prefcount == 15 ? 16 : prefcount);
-       postcount = (postcount == 15 ? 16 : postcount);
-
-       if (lladdr)
-               lowpan_raw_dump_inline(__func__, "linklocal address",
-                                               lladdr, IEEE802154_ADDR_LEN);
-       if (prefcount > 0)
-               memcpy(ipaddr, prefix, prefcount);
-
-       if (postcount > 0) {
-               memcpy(&ipaddr->s6_addr[16 - postcount], skb->data, postcount);
-               skb_pull(skb, postcount);
-       } else if (prefcount > 0) {
-               if (lladdr == NULL)
+       switch (address_mode) {
+       case LOWPAN_IPHC_ADDR_00:
+               /*
+                * for global link addresses
+                */
+               memcpy(ipaddr->s6_addr, skb->data, 16);
+               skb_pull(skb, 16);
+               break;
+       case LOWPAN_IPHC_ADDR_01:
+               /*
+                * fe:80::XXXX:XXXX:XXXX:XXXX
+                */
+               ipaddr->s6_addr[0] = 0xFE;
+               ipaddr->s6_addr[1] = 0x80;
+               memcpy(&ipaddr->s6_addr[8], skb->data, 8);
+               skb_pull(skb, 8);
+               break;
+       case LOWPAN_IPHC_ADDR_02:
+               /*
+                * fe:80::ff:fe00:XXXX
+                */
+               ipaddr->s6_addr[0] = 0xFE;
+               ipaddr->s6_addr[1] = 0x80;
+               ipaddr->s6_addr[11] = 0xFF;
+               ipaddr->s6_addr[12] = 0xFE;
+               memcpy(&ipaddr->s6_addr[14], skb->data, 2);
+               skb_pull(skb, 2);
+               break;
+       case LOWPAN_IPHC_ADDR_03:
+               switch (lladdr->addr_type) {
+               case IEEE802154_ADDR_LONG:
+                       /*
+                        * fe:80::XXXX:XXXX:XXXX:XXXX
+                        *        \_________________/
+                        *              lladdr
+                        */
+                       ipaddr->s6_addr[0] = 0xFE;
+                       ipaddr->s6_addr[1] = 0x80;
+                       memcpy(&ipaddr->s6_addr[8], lladdr->hwaddr,
+                                       IEEE802154_ADDR_LEN);
+                       /*
+                        * second bit-flip (Universe/Local)
+                        * is done according RFC2464
+                        */
+                       ipaddr->s6_addr[8] ^= 0x02;
+                       break;
+               case IEEE802154_ADDR_SHORT:
+                       /*
+                        * fe:80::ff:fe00:XXXX
+                        *                \__/
+                        *             short_addr
+                        *
+                        * Universe/Local bit is zero.
+                        */
+                       ipaddr->s6_addr[0] = 0xFE;
+                       ipaddr->s6_addr[1] = 0x80;
+                       ipaddr->s6_addr[11] = 0xFF;
+                       ipaddr->s6_addr[12] = 0xFE;
+                       memset(&ipaddr->s6_addr[14], lladdr->short_addr, 2);
+                       break;
+               default:
+                       pr_debug("Invalid addr_type set\n");
                        return -EINVAL;
-
-               /* no IID based configuration if no prefix and no data */
-               lowpan_uip_ds6_set_addr_iid(ipaddr, lladdr);
+               }
+               break;
+       default:
+               pr_debug("Invalid address mode value: 0x%x\n", address_mode);
+               return -EINVAL;
        }
 
-       pr_debug("uncompressing %d + %d => ", prefcount, postcount);
+       pr_debug("Reconstructed ipv6 addr is:\n");
        lowpan_raw_dump_inline(NULL, NULL, ipaddr->s6_addr, 16);
 
        return 0;
@@ -779,8 +794,8 @@ static int
 lowpan_process_data(struct sk_buff *skb)
 {
        struct ipv6hdr hdr = {};
-       u8 tmp, iphc0, iphc1, num_context = 0;
-       u8 *_saddr, *_daddr;
+       u8 tmp, iphc0, iphc1;
+       const struct ieee802154_addr *_saddr, *_daddr;
        int err;
 
        lowpan_raw_dump_table(__func__, "raw skb data dump", skb->data,
@@ -884,8 +899,8 @@ lowpan_process_data(struct sk_buff *skb)
        if (lowpan_fetch_skb_u8(skb, &iphc1))
                goto drop;
 
-       _saddr = mac_cb(skb)->sa.hwaddr;
-       _daddr = mac_cb(skb)->da.hwaddr;
+       _saddr = &mac_cb(skb)->sa;
+       _daddr = &mac_cb(skb)->da;
 
        pr_debug("iphc0 = %02x, iphc1 = %02x\n", iphc0, iphc1);
 
@@ -967,8 +982,7 @@ lowpan_process_data(struct sk_buff *skb)
 
        /* Source address uncompression */
        pr_debug("source address stateless compression\n");
-       err = lowpan_uncompress_addr(skb, &hdr.saddr, lowpan_llprefix,
-                               lowpan_unc_llconf[tmp], _saddr);
+       err = lowpan_uncompress_addr(skb, &hdr.saddr, tmp, _saddr);
        if (err)
                goto drop;
 
@@ -988,8 +1002,7 @@ lowpan_process_data(struct sk_buff *skb)
                }
        } else {
                pr_debug("dest: stateless compression\n");
-               err = lowpan_uncompress_addr(skb, &hdr.daddr, lowpan_llprefix,
-                               lowpan_unc_llconf[tmp], _daddr);
+               err = lowpan_uncompress_addr(skb, &hdr.daddr, tmp, _daddr);
                if (err)
                        goto drop;
        }
diff --git a/net/ieee802154/6lowpan.h b/net/ieee802154/6lowpan.h
index a4a307b..b565120 100644
--- a/net/ieee802154/6lowpan.h
+++ b/net/ieee802154/6lowpan.h
@@ -196,10 +196,12 @@
 /* Values of fields within the IPHC encoding second byte */
 #define LOWPAN_IPHC_CID                0x80
 
+#define LOWPAN_IPHC_ADDR_00    0x00
+#define LOWPAN_IPHC_ADDR_01    0x01
+#define LOWPAN_IPHC_ADDR_02    0x02
+#define LOWPAN_IPHC_ADDR_03    0x03
+
 #define LOWPAN_IPHC_SAC                0x40
-#define LOWPAN_IPHC_SAM_00     0x00
-#define LOWPAN_IPHC_SAM_01     0x10
-#define LOWPAN_IPHC_SAM_10     0x20
 #define LOWPAN_IPHC_SAM                0x30
 
 #define LOWPAN_IPHC_SAM_BIT    4
-- 
1.8.3.3


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