net: 6lowpan: use array for find nhc id

This patch will remove the complete overengineered and overthinking rb data
structure for looking up the nhc by nhcid. Instead we using the existing
nhc next header array and iterate over it. It works now for 1 byte values
only. However there are only 1 byte nhc id values currently
supported and IANA also does not specify large than 1 byte values yet.
If there are 2 byte values for nhc ids specified we can revisit this
data structure and add support for it.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Reviewed-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Link: https://lore.kernel.org/r/20220428030534.3220410-3-aahringo@redhat.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

1 files changed, 13 insertions, 78 deletions

diff --git a/net/6lowpan/nhc.c b/net/6lowpan/nhc.c
index d6bbbd4ab38b..019f121b2449 100644
--- a/net/6lowpan/nhc.c
+++ b/net/6lowpan/nhc.c
@@ -12,77 +12,26 @@
 
 #include "nhc.h"
 
-static struct rb_root rb_root = RB_ROOT;
 static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX + 1];
 static DEFINE_SPINLOCK(lowpan_nhc_lock);
 
-static int lowpan_nhc_insert(struct lowpan_nhc *nhc)
+static struct lowpan_nhc *lowpan_nhc_by_nhcid(struct sk_buff *skb)
 {
-	struct rb_node **new = &rb_root.rb_node, *parent = NULL;
-
-	/* Figure out where to put new node */
-	while (*new) {
-		struct lowpan_nhc *this = rb_entry(*new, struct lowpan_nhc,
-						   node);
-		int result, len_dif, len;
-
-		len_dif = nhc->idlen - this->idlen;
-
-		if (nhc->idlen < this->idlen)
-			len = nhc->idlen;
-		else
-			len = this->idlen;
-
-		result = memcmp(nhc->id, this->id, len);
-		if (!result)
-			result = len_dif;
-
-		parent = *new;
-		if (result < 0)
-			new = &((*new)->rb_left);
-		else if (result > 0)
-			new = &((*new)->rb_right);
-		else
-			return -EEXIST;
-	}
+	struct lowpan_nhc *nhc;
+	int i;
+	u8 id;
 
-	/* Add new node and rebalance tree. */
-	rb_link_node(&nhc->node, parent, new);
-	rb_insert_color(&nhc->node, &rb_root);
+	if (!pskb_may_pull(skb, 1))
+		return NULL;
 
-	return 0;
-}
+	id = *skb->data;
 
-static void lowpan_nhc_remove(struct lowpan_nhc *nhc)
-{
-	rb_erase(&nhc->node, &rb_root);
-}
+	for (i = 0; i < NEXTHDR_MAX + 1; i++) {
+		nhc = lowpan_nexthdr_nhcs[i];
+		if (!nhc)
+			continue;
 
-static struct lowpan_nhc *lowpan_nhc_by_nhcid(const struct sk_buff *skb)
-{
-	struct rb_node *node = rb_root.rb_node;
-	const u8 *nhcid_skb_ptr = skb->data;
-
-	while (node) {
-		struct lowpan_nhc *nhc = rb_entry(node, struct lowpan_nhc,
-						  node);
-		u8 nhcid_skb_ptr_masked[LOWPAN_NHC_MAX_ID_LEN];
-		int result, i;
-
-		if (nhcid_skb_ptr + nhc->idlen > skb->data + skb->len)
-			return NULL;
-
-		/* copy and mask afterwards the nhid value from skb */
-		memcpy(nhcid_skb_ptr_masked, nhcid_skb_ptr, nhc->idlen);
-		for (i = 0; i < nhc->idlen; i++)
-			nhcid_skb_ptr_masked[i] &= nhc->idmask[i];
-
-		result = memcmp(nhcid_skb_ptr_masked, nhc->id, nhc->idlen);
-		if (result < 0)
-			node = node->rb_left;
-		else if (result > 0)
-			node = node->rb_right;
-		else
+		if ((id & nhc->idmask) == nhc->id)
 			return nhc;
 	}
 
@@ -191,16 +140,7 @@ int lowpan_nhc_do_uncompression(struct sk_buff *skb,
 
 int lowpan_nhc_add(struct lowpan_nhc *nhc)
 {
-	int ret;
-
-	if (!nhc->idlen || !nhc->idsetup)
-		return -EINVAL;
-
-	WARN_ONCE(nhc->idlen > LOWPAN_NHC_MAX_ID_LEN,
-		  "LOWPAN_NHC_MAX_ID_LEN should be updated to %zd.\n",
-		  nhc->idlen);
-
-	nhc->idsetup(nhc);
+	int ret = 0;
 
 	spin_lock_bh(&lowpan_nhc_lock);
 
@@ -209,10 +149,6 @@ int lowpan_nhc_add(struct lowpan_nhc *nhc)
 		goto out;
 	}
 
-	ret = lowpan_nhc_insert(nhc);
-	if (ret < 0)
-		goto out;
-
 	lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
 out:
 	spin_unlock_bh(&lowpan_nhc_lock);
@@ -224,7 +160,6 @@ void lowpan_nhc_del(struct lowpan_nhc *nhc)
 {
 	spin_lock_bh(&lowpan_nhc_lock);
 
-	lowpan_nhc_remove(nhc);
 	lowpan_nexthdr_nhcs[nhc->nexthdr] = NULL;
 
 	spin_unlock_bh(&lowpan_nhc_lock);