netdev - [PATCH wpan-next 2/2] 6lowpan: nhc: drop EEXIST limitation

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Date:   Sun, 12 Jun 2022 23:29:22 -0400
From:   Alexander Aring <aahringo@...hat.com>
To:     stefan@...enfreihafen.org
Cc:     linux-wpan@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        netdev@...r.kernel.org, aahringo@...hat.com
Subject: [PATCH wpan-next 2/2] 6lowpan: nhc: drop EEXIST limitation

In nhc we have compression() and uncompression(). Currently we have a
limitation that we return -EEXIST when it's the nhc is already
registered according the nexthdr. But on receiving handling and the
nhcid we can indeed support both at the same time. We remove the current
static array implementation and replace it by a dynamic list handling to
get rid of this limitation.

Signed-off-by: Alexander Aring <aahringo@...hat.com>
---
 net/6lowpan/nhc.c | 69 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 44 insertions(+), 25 deletions(-)

diff --git a/net/6lowpan/nhc.c b/net/6lowpan/nhc.c
index 7b374595328d..3d7c50139142 100644
--- a/net/6lowpan/nhc.c
+++ b/net/6lowpan/nhc.c
@@ -12,13 +12,30 @@
 
 #include "nhc.h"
 
-static const struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX + 1];
+struct lowpan_nhc_entry {
+	const struct lowpan_nhc *nhc;
+	struct list_head list;
+};
+
 static DEFINE_SPINLOCK(lowpan_nhc_lock);
+static LIST_HEAD(lowpan_nexthdr_nhcs);
+
+const struct lowpan_nhc *lowpan_nhc_by_nexthdr(u8 nexthdr)
+{
+	const struct lowpan_nhc_entry *e;
+
+	list_for_each_entry(e, &lowpan_nexthdr_nhcs, list) {
+		if (e->nhc->nexthdr == nexthdr &&
+		    e->nhc->compress)
+			return e->nhc;
+	}
+
+	return NULL;
+}
 
 static const struct lowpan_nhc *lowpan_nhc_by_nhcid(struct sk_buff *skb)
 {
-	const struct lowpan_nhc *nhc;
-	int i;
+	const struct lowpan_nhc_entry *e;
 	u8 id;
 
 	if (!pskb_may_pull(skb, 1))
@@ -26,13 +43,9 @@ static const struct lowpan_nhc *lowpan_nhc_by_nhcid(struct sk_buff *skb)
 
 	id = *skb->data;
 
-	for (i = 0; i < NEXTHDR_MAX + 1; i++) {
-		nhc = lowpan_nexthdr_nhcs[i];
-		if (!nhc)
-			continue;
-
-		if ((id & nhc->idmask) == nhc->id)
-			return nhc;
+	list_for_each_entry(e, &lowpan_nexthdr_nhcs, list) {
+		if ((id & e->nhc->idmask) == e->nhc->id)
+			return e->nhc;
 	}
 
 	return NULL;
@@ -46,8 +59,8 @@ int lowpan_nhc_check_compression(struct sk_buff *skb,
 
 	spin_lock_bh(&lowpan_nhc_lock);
 
-	nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
-	if (!(nhc && nhc->compress))
+	nhc = lowpan_nhc_by_nexthdr(hdr->nexthdr);
+	if (!nhc)
 		ret = -ENOENT;
 
 	spin_unlock_bh(&lowpan_nhc_lock);
@@ -63,7 +76,7 @@ int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr *hdr,
 
 	spin_lock_bh(&lowpan_nhc_lock);
 
-	nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
+	nhc = lowpan_nhc_by_nexthdr(hdr->nexthdr);
 	/* check if the nhc module was removed in unlocked part.
 	 * TODO: this is a workaround we should prevent unloading
 	 * of nhc modules while unlocked part, this will always drop
@@ -140,28 +153,34 @@ int lowpan_nhc_do_uncompression(struct sk_buff *skb,
 
 int lowpan_nhc_add(const struct lowpan_nhc *nhc)
 {
-	int ret = 0;
+	struct lowpan_nhc_entry *e;
 
-	spin_lock_bh(&lowpan_nhc_lock);
+	e = kmalloc(sizeof(*e), GFP_KERNEL);
+	if (!e)
+		return -ENOMEM;
 
-	if (lowpan_nexthdr_nhcs[nhc->nexthdr]) {
-		ret = -EEXIST;
-		goto out;
-	}
+	e->nhc = nhc;
 
-	lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
-out:
+	spin_lock_bh(&lowpan_nhc_lock);
+	list_add(&e->list, &lowpan_nexthdr_nhcs);
 	spin_unlock_bh(&lowpan_nhc_lock);
-	return ret;
+
+	return 0;
 }
 EXPORT_SYMBOL(lowpan_nhc_add);
 
 void lowpan_nhc_del(const struct lowpan_nhc *nhc)
 {
-	spin_lock_bh(&lowpan_nhc_lock);
-
-	lowpan_nexthdr_nhcs[nhc->nexthdr] = NULL;
+	struct lowpan_nhc_entry *e, *tmp;
 
+	spin_lock_bh(&lowpan_nhc_lock);
+	list_for_each_entry_safe(e, tmp, &lowpan_nexthdr_nhcs, list) {
+		if (e->nhc == nhc) {
+			list_del(&e->list);
+			kfree(e);
+			break;
+		}
+	}
 	spin_unlock_bh(&lowpan_nhc_lock);
 
 	synchronize_net();
-- 
2.31.1