6lowpan: add generic nhc layer interface
This patch adds a generic next header compression layer interface. There
exists various methods to do a header compression after 6LoWPAN header
to save payload. This introduce a generic nhc header which allow a
simple adding of a new header compression format instead of a static
implementation inside the 6LoWPAN header compression and uncompression
function.
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Cc: Martin Townsend <mtownsend1973@gmail.com>
Reviewed-by: Stefan Schmidt <s.schmidt@samsung.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/6lowpan/nhc.c b/net/6lowpan/nhc.c
new file mode 100644
index 0000000..fd20fc5
--- /dev/null
+++ b/net/6lowpan/nhc.c
@@ -0,0 +1,241 @@
+/*
+ * 6LoWPAN next header compression
+ *
+ *
+ * Authors:
+ * Alexander Aring <aar@pengutronix.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <linux/netdevice.h>
+
+#include <net/ipv6.h>
+
+#include "nhc.h"
+
+static struct rb_root rb_root = RB_ROOT;
+static struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX];
+static DEFINE_SPINLOCK(lowpan_nhc_lock);
+
+static int lowpan_nhc_insert(struct lowpan_nhc *nhc)
+{
+ struct rb_node **new = &rb_root.rb_node, *parent = NULL;
+
+ /* Figure out where to put new node */
+ while (*new) {
+ struct lowpan_nhc *this = container_of(*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;
+ }
+
+ /* Add new node and rebalance tree. */
+ rb_link_node(&nhc->node, parent, new);
+ rb_insert_color(&nhc->node, &rb_root);
+
+ return 0;
+}
+
+static void lowpan_nhc_remove(struct lowpan_nhc *nhc)
+{
+ rb_erase(&nhc->node, &rb_root);
+}
+
+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 = container_of(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
+ return nhc;
+ }
+
+ return NULL;
+}
+
+int lowpan_nhc_check_compression(struct sk_buff *skb,
+ const struct ipv6hdr *hdr, u8 **hc_ptr,
+ u8 *iphc0)
+{
+ struct lowpan_nhc *nhc;
+
+ spin_lock_bh(&lowpan_nhc_lock);
+
+ nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
+ if (nhc && nhc->compress)
+ *iphc0 |= LOWPAN_IPHC_NH_C;
+ else
+ lowpan_push_hc_data(hc_ptr, &hdr->nexthdr,
+ sizeof(hdr->nexthdr));
+
+ spin_unlock_bh(&lowpan_nhc_lock);
+
+ return 0;
+}
+
+int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr *hdr,
+ u8 **hc_ptr)
+{
+ int ret;
+ 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, struct net_device *dev,
+ struct ipv6hdr *hdr)
+{
+ 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(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);
+
+ spin_lock_bh(&lowpan_nhc_lock);
+
+ if (lowpan_nexthdr_nhcs[nhc->nexthdr]) {
+ ret = -EEXIST;
+ 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);
+ return ret;
+}
+EXPORT_SYMBOL(lowpan_nhc_add);
+
+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);
+
+ synchronize_net();
+}
+EXPORT_SYMBOL(lowpan_nhc_del);