1 files changed, 169 insertions, 0 deletions
diff --git a/net/6lowpan/nhc.c b/net/6lowpan/nhc.c
new file mode 100644
index 000000000..7b3745953
--- /dev/null
+++ b/net/6lowpan/nhc.c
@@ -0,0 +1,169 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *	6LoWPAN next header compression
+ *
+ *	Authors:
+ *	Alexander Aring		<aar@pengutronix.de>
+ */
+
+#include <linux/netdevice.h>
+
+#include <net/ipv6.h>
+
+#include "nhc.h"
+
+static const struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX + 1];
+static DEFINE_SPINLOCK(lowpan_nhc_lock);
+
+static const struct lowpan_nhc *lowpan_nhc_by_nhcid(struct sk_buff *skb)
+{
+	const struct lowpan_nhc *nhc;
+	int i;
+	u8 id;
+
+	if (!pskb_may_pull(skb, 1))
+		return NULL;
+
+	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;
+	}
+
+	return NULL;
+}
+
+int lowpan_nhc_check_compression(struct sk_buff *skb,
+				 const struct ipv6hdr *hdr, u8 **hc_ptr)
+{
+	const struct lowpan_nhc *nhc;
+	int ret = 0;
+
+	spin_lock_bh(&lowpan_nhc_lock);
+
+	nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
+	if (!(nhc && nhc->compress))
+		ret = -ENOENT;
+
+	spin_unlock_bh(&lowpan_nhc_lock);
+
+	return ret;
+}
+
+int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr *hdr,
+			      u8 **hc_ptr)
+{
+	int ret;
+	const struct lowpan_nhc *nhc;
+
+	spin_lock_bh(&lowpan_nhc_lock);
+
+	nhc = lowpan_nexthdr_nhcs[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
+	 * the lowpan packet but it's very unlikely.
+	 *
+	 * Solution isn't easy because we need to decide at
+	 * lowpan_nhc_check_compression if we do a compression or not.
+	 * Because the inline data which is added to skb, we can't move this
+	 * handling.
+	 */
+	if (unlikely(!nhc || !nhc->compress)) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	/* In the case of RAW sockets the transport header is not set by
+	 * the ip6 stack so we must set it ourselves
+	 */
+	if (skb->transport_header == skb->network_header)
+		skb_set_transport_header(skb, sizeof(struct ipv6hdr));
+
+	ret = nhc->compress(skb, hc_ptr);
+	if (ret < 0)
+		goto out;
+
+	/* skip the transport header */
+	skb_pull(skb, nhc->nexthdrlen);
+
+out:
+	spin_unlock_bh(&lowpan_nhc_lock);
+
+	return ret;
+}
+
+int lowpan_nhc_do_uncompression(struct sk_buff *skb,
+				const struct net_device *dev,
+				struct ipv6hdr *hdr)
+{
+	const struct lowpan_nhc *nhc;
+	int ret;
+
+	spin_lock_bh(&lowpan_nhc_lock);
+
+	nhc = lowpan_nhc_by_nhcid(skb);
+	if (nhc) {
+		if (nhc->uncompress) {
+			ret = nhc->uncompress(skb, sizeof(struct ipv6hdr) +
+					      nhc->nexthdrlen);
+			if (ret < 0) {
+				spin_unlock_bh(&lowpan_nhc_lock);
+				return ret;
+			}
+		} else {
+			spin_unlock_bh(&lowpan_nhc_lock);
+			netdev_warn(dev, "received nhc id for %s which is not implemented.\n",
+				    nhc->name);
+			return -ENOTSUPP;
+		}
+	} else {
+		spin_unlock_bh(&lowpan_nhc_lock);
+		netdev_warn(dev, "received unknown nhc id which was not found.\n");
+		return -ENOENT;
+	}
+
+	hdr->nexthdr = nhc->nexthdr;
+	skb_reset_transport_header(skb);
+	raw_dump_table(__func__, "raw transport header dump",
+		       skb_transport_header(skb), nhc->nexthdrlen);
+
+	spin_unlock_bh(&lowpan_nhc_lock);
+
+	return 0;
+}
+
+int lowpan_nhc_add(const struct lowpan_nhc *nhc)
+{
+	int ret = 0;
+
+	spin_lock_bh(&lowpan_nhc_lock);
+
+	if (lowpan_nexthdr_nhcs[nhc->nexthdr]) {
+		ret = -EEXIST;
+		goto out;
+	}
+
+	lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
+out:
+	spin_unlock_bh(&lowpan_nhc_lock);
+	return ret;
+}
+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;
+
+	spin_unlock_bh(&lowpan_nhc_lock);
+
+	synchronize_net();
+}
+EXPORT_SYMBOL(lowpan_nhc_del);