[RFC bluetooth-next 0/4] 6lowpan: debugfs and stateful compression support

[RFC bluetooth-next 0/4] 6lowpan: debugfs and stateful compression support

[Alexander Aring]

Hi,

This patch based on the work of Lukasz Duda. It doesn't contain any interface
lookup methods since we have a generic private dataroom per 6lowpan interface.

Also I dropped the list implementation and do a simple array one. It also
contains support for multicast stateful compression.

To access the context we supporting a complete callback structure for
operations, the include/net/6lowpan.h header contains static inline functions
to call these operations. With such behaviour we don't get any module
dependencies if we need upcomming runtime decisions inside the IPv6 stack.
The alternative would be to do everything inside static inline functions, but
there are few different to handling unicast and multicast context id's, so
it's maybe better to do this as "ops callback structure".

Few things which I am not sure about if it's correct:
 - I implement the dci multicast context table and dci unicast as different
   table. I don't know if when I have a context id "6" which is multicast
   then, I don't can have a unicast context id which is "6". I think they are
   different and we can indicate which table we need to use by the IPHC M bit
   (receiving side)  or the multicast address scope (transmit side).
 - Unicast context prefix length can be shorter than 64 bits. Yes this can be,
   but if somebody wants to do that he usually means "expand the bits until 64
   with zeros". I forbid to add prefix below 64 bits for now.
   Each stateful compression has cases for the IID bits (last 8 byte, use it as
   inline data/do compression, etc.). When I have a prefix 2000:: with prefix
   length 16, then I we hit the case of "Any remaining bits are zero." of
   stateful compression, this means it can be converted by "2000::" prefix
   length 64, then we don't need to care about that when doing a lookup of
   context.
 - I tried to get wireshark know about the available context without success.
   What I successful get working is tell prefix length exact 64 bits long. I
   don't know if wireshark do a correct context handling here, but it's also
   possible to have a prefix length above 64 (In my opinion). E.g. unicast
   stateful compression in case of SAM/DAM 01:
   "Bits covered by context information are always used.  Any IID bits not
    covered by context information are taken directly from the corresponding
    bits carried in-line.

   This patch series do following handling for this case:
   1. generate ipv6 address with inline IID data.
   2. copy the prefix bits from context to the address, which _maybe_ overwrite
      the IID (last eight bytes) data which was carried as inline data.

   This means, if my context is a full address 2001::1/128, then it will be
   the case of SAM/DAM = 11, which means the address is fully elided. (Don't
   care about the IID bits, which will be reconstructed from encapsulating
   header.

   All others SAM/DAM cases has a similar handling.

   Nevertheless I don't know how I can tell that wireshark, I can tell prefix which
   are 64 bit's long only.

Any comments are welcome.

- Alex

Alexander Aring (4):
  6lowpan: add debugfs support
  6lowpan: iphc: add check for reserved values
  6lowpan: iphc: remove handling when dam is zero
  6lowpan: iphc: add support for stateful compression

 include/net/6lowpan.h         |  64 ++++-
 net/6lowpan/6lowpan_i.h       |  28 +++
 net/6lowpan/Kconfig           |   7 +
 net/6lowpan/Makefile          |   1 +
 net/6lowpan/core.c            |  36 ++-
 net/6lowpan/debugfs.c         | 158 ++++++++++++
 net/6lowpan/iphc.c            | 542 +++++++++++++++++++++++++++++++++++++-----
 net/bluetooth/6lowpan.c       |  17 +-
 net/ieee802154/6lowpan/core.c |  14 +-
 9 files changed, 793 insertions(+), 74 deletions(-)
 create mode 100644 net/6lowpan/6lowpan_i.h
 create mode 100644 net/6lowpan/debugfs.c

-- 
2.6.1

[RFC bluetooth-next 1/4] 6lowpan: add debugfs support

[Alexander Aring]

This patch will introduce a 6lowpan entry into the debugfs if enabled.
Inside this 6lowpan directory we create a subdirectories of all 6lowpan
interfaces to offer a per interface debugfs support.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
---
 include/net/6lowpan.h         |  2 +-
 net/6lowpan/6lowpan_i.h       | 25 +++++++++++++++++++++
 net/6lowpan/Kconfig           |  7 ++++++
 net/6lowpan/Makefile          |  1 +
 net/6lowpan/core.c            | 19 +++++++++++++++-
 net/6lowpan/debugfs.c         | 51 +++++++++++++++++++++++++++++++++++++++++++
 net/bluetooth/6lowpan.c       | 17 +++++++++------
 net/ieee802154/6lowpan/core.c | 14 +++++++-----
 8 files changed, 122 insertions(+), 14 deletions(-)
 create mode 100644 net/6lowpan/6lowpan_i.h
 create mode 100644 net/6lowpan/debugfs.c

diff --git a/include/net/6lowpan.h b/include/net/6lowpan.h
index cf3bc56..edce9a1 100644
--- a/include/net/6lowpan.h
+++ b/include/net/6lowpan.h
@@ -185,7 +185,7 @@ static inline void lowpan_push_hc_data(u8 **hc_ptr, const void *data,
 	*hc_ptr += len;
 }
 
-void lowpan_netdev_setup(struct net_device *dev, enum lowpan_lltypes lltype);
+int lowpan_netdev_setup(struct net_device *dev, enum lowpan_lltypes lltype);
 
 /**
  * lowpan_header_decompress - replace 6LoWPAN header with IPv6 header
diff --git a/net/6lowpan/6lowpan_i.h b/net/6lowpan/6lowpan_i.h
new file mode 100644
index 0000000..102c2a4
--- /dev/null
+++ b/net/6lowpan/6lowpan_i.h
@@ -0,0 +1,25 @@
+#ifndef __6LOWPAN_I_H
+#define __6LOWPAN_I_H
+
+#include <linux/netdevice.h>
+
+#ifdef CONFIG_6LOWPAN_DEBUGFS
+int lowpan_dev_debugfs_init(struct net_device *dev);
+
+int __init lowpan_debugfs_init(void);
+void lowpan_debugfs_exit(void);
+#else
+static inline int lowpan_dev_debugfs_init(struct net_device *dev)
+{
+	return 0;
+}
+
+static inline int __init lowpan_debugfs_init(void)
+{
+	return 0;
+}
+
+static inline void lowpan_debugfs_exit(void) { }
+#endif /* CONFIG_6LOWPAN_DEBUGFS */
+
+#endif /* __6LOWPAN_I_H */
diff --git a/net/6lowpan/Kconfig b/net/6lowpan/Kconfig
index 7fa0f38..01c901c 100644
--- a/net/6lowpan/Kconfig
+++ b/net/6lowpan/Kconfig
@@ -5,6 +5,13 @@ menuconfig 6LOWPAN
 	  This enables IPv6 over Low power Wireless Personal Area Network -
 	  "6LoWPAN" which is supported by IEEE 802.15.4 or Bluetooth stacks.
 
+config 6LOWPAN_DEBUGFS
+	bool "6LoWPAN debugfs support"
+	depends on 6LOWPAN
+	---help---
+	  This enables 6LoWPAN debugfs support. For example to manipulate
+	  IPHC context information at runtime.
+
 menuconfig 6LOWPAN_NHC
 	tristate "Next Header Compression Support"
 	depends on 6LOWPAN
diff --git a/net/6lowpan/Makefile b/net/6lowpan/Makefile
index c6ffc55..54cad8d 100644
--- a/net/6lowpan/Makefile
+++ b/net/6lowpan/Makefile
@@ -1,6 +1,7 @@
 obj-$(CONFIG_6LOWPAN) += 6lowpan.o
 
 6lowpan-y := core.o iphc.o nhc.o
+6lowpan-$(CONFIG_6LOWPAN_DEBUGFS) += debugfs.o
 
 #rfc6282 nhcs
 obj-$(CONFIG_6LOWPAN_NHC_DEST) += nhc_dest.o
diff --git a/net/6lowpan/core.c b/net/6lowpan/core.c
index 83b19e0..7f46c7e 100644
--- a/net/6lowpan/core.c
+++ b/net/6lowpan/core.c
@@ -15,7 +15,9 @@
 
 #include <net/6lowpan.h>
 
-void lowpan_netdev_setup(struct net_device *dev, enum lowpan_lltypes lltype)
+#include "6lowpan_i.h"
+
+int lowpan_netdev_setup(struct net_device *dev, enum lowpan_lltypes lltype)
 {
 	dev->addr_len = EUI64_ADDR_LEN;
 	dev->type = ARPHRD_6LOWPAN;
@@ -23,11 +25,19 @@ void lowpan_netdev_setup(struct net_device *dev, enum lowpan_lltypes lltype)
 	dev->priv_flags |= IFF_NO_QUEUE;
 
 	lowpan_priv(dev)->lltype = lltype;
+
+	return lowpan_dev_debugfs_init(dev);
 }
 EXPORT_SYMBOL(lowpan_netdev_setup);
 
 static int __init lowpan_module_init(void)
 {
+	int ret;
+
+	ret = lowpan_debugfs_init();
+	if (ret < 0)
+		return ret;
+
 	request_module_nowait("ipv6");
 
 	request_module_nowait("nhc_dest");
@@ -40,6 +50,13 @@ static int __init lowpan_module_init(void)
 
 	return 0;
 }
+
+static void __exit lowpan_module_exit(void)
+{
+	lowpan_debugfs_exit();
+}
+
 module_init(lowpan_module_init);
+module_exit(lowpan_module_exit);
 
 MODULE_LICENSE("GPL");
diff --git a/net/6lowpan/debugfs.c b/net/6lowpan/debugfs.c
new file mode 100644
index 0000000..e70eee4
--- /dev/null
+++ b/net/6lowpan/debugfs.c
@@ -0,0 +1,51 @@
+/* This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Authors:
+ * (C) 2015 Pengutronix, Alexander Aring <aar@pengutronix.de>
+ * Copyright (c)  2015 Nordic Semiconductor. All Rights Reserved.
+ */
+
+#include <linux/debugfs.h>
+
+#include <net/6lowpan.h>
+
+#include "6lowpan_i.h"
+
+static struct dentry *lowpan_debugfs;
+
+int lowpan_dev_debugfs_init(struct net_device *dev)
+{
+	static struct dentry *iface;
+
+	/* creating the root */
+	iface = debugfs_create_dir(dev->name, lowpan_debugfs);
+	if (!iface)
+		goto fail;
+
+	return 0;
+
+fail:
+	lowpan_debugfs_exit();
+	return -EINVAL;
+}
+
+int __init lowpan_debugfs_init(void)
+{
+	lowpan_debugfs = debugfs_create_dir("6lowpan", NULL);
+	if (!lowpan_debugfs)
+		return -EINVAL;
+
+	return 0;
+}
+
+void lowpan_debugfs_exit(void)
+{
+	debugfs_remove_recursive(lowpan_debugfs);
+}
diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
index 9e9cca3..57aa5ff 100644
--- a/net/bluetooth/6lowpan.c
+++ b/net/bluetooth/6lowpan.c
@@ -825,16 +825,14 @@ static int setup_netdev(struct l2cap_chan *chan, struct lowpan_dev **dev)
 	list_add_rcu(&(*dev)->list, &bt_6lowpan_devices);
 	spin_unlock(&devices_lock);
 
-	lowpan_netdev_setup(netdev, LOWPAN_LLTYPE_BTLE);
+	err = lowpan_netdev_setup(netdev, LOWPAN_LLTYPE_BTLE);
+	if (err < 0)
+		goto free_netdev;
 
 	err = register_netdev(netdev);
 	if (err < 0) {
 		BT_INFO("register_netdev failed %d", err);
-		spin_lock(&devices_lock);
-		list_del_rcu(&(*dev)->list);
-		spin_unlock(&devices_lock);
-		free_netdev(netdev);
-		goto out;
+		goto free_netdev;
 	}
 
 	BT_DBG("ifindex %d peer bdaddr %pMR type %d my addr %pMR type %d",
@@ -844,7 +842,12 @@ static int setup_netdev(struct l2cap_chan *chan, struct lowpan_dev **dev)
 
 	return 0;
 
-out:
+free_netdev:
+	spin_lock(&devices_lock);
+	list_del_rcu(&(*dev)->list);
+	spin_unlock(&devices_lock);
+	free_netdev(netdev);
+
 	return err;
 }
 
diff --git a/net/ieee802154/6lowpan/core.c b/net/ieee802154/6lowpan/core.c
index 20c49c7..67ed7dc 100644
--- a/net/ieee802154/6lowpan/core.c
+++ b/net/ieee802154/6lowpan/core.c
@@ -161,16 +161,20 @@ static int lowpan_newlink(struct net *src_net, struct net_device *ldev,
 				wdev->needed_headroom;
 	ldev->needed_tailroom = wdev->needed_tailroom;
 
-	lowpan_netdev_setup(ldev, LOWPAN_LLTYPE_IEEE802154);
+	ret = lowpan_netdev_setup(ldev, LOWPAN_LLTYPE_IEEE802154);
+	if (ret < 0)
+		goto dev_put;
 
 	ret = register_netdevice(ldev);
-	if (ret < 0) {
-		dev_put(wdev);
-		return ret;
-	}
+	if (ret < 0)
+		goto dev_put;
 
 	wdev->ieee802154_ptr->lowpan_dev = ldev;
 	return 0;
+
+dev_put:
+	dev_put(wdev);
+	return ret;
 }
 
 static void lowpan_dellink(struct net_device *ldev, struct list_head *head)
-- 
2.6.1

Re: [RFC bluetooth-next 1/4] 6lowpan: add debugfs support

[Alexander Aring]

On Wed, Nov 11, 2015 at 06:14:36PM +0100, Alexander Aring wrote:
...
> +config 6LOWPAN_DEBUGFS
> +	bool "6LoWPAN debugfs support"
> +	depends on 6LOWPAN

missing:

depends on DEBUG_FS

> +	---help---
> +	  This enables 6LoWPAN debugfs support. For example to manipulate
> +	  IPHC context information at runtime.
> +
>  menuconfig 6LOWPAN_NHC
>  	tristate "Next Header Compression Support"
>  	depends on 6LOWPAN
> diff --git a/net/6lowpan/Makefile b/net/6lowpan/Makefile
> index c6ffc55..54cad8d 100644
> --- a/net/6lowpan/Makefile
> +++ b/net/6lowpan/Makefile
> @@ -1,6 +1,7 @@
>  obj-$(CONFIG_6LOWPAN) += 6lowpan.o
>  
>  6lowpan-y := core.o iphc.o nhc.o
> +6lowpan-$(CONFIG_6LOWPAN_DEBUGFS) += debugfs.o
...
> +
> +int lowpan_dev_debugfs_init(struct net_device *dev)
> +{
> +	static struct dentry *iface;
> +
> +	/* creating the root */
> +	iface = debugfs_create_dir(dev->name, lowpan_debugfs);
> +	if (!iface)
> +		goto fail;
> +
> +	return 0;
> +
> +fail:
> +	lowpan_debugfs_exit();

This is broken, this will delete everything also the
"$DEBUGFS_MOUNTPOINT/6lowpan" directory. What we need is a
debugfs_remove_recursive(iface); call here, which deletes everything
which is registered at iface dentry.

Also we need to call this when a lowpan interface will be unregistered,
otherwise we have still the debugfs entries when an interface doesn't
exist anymore.

I will fix this issues for the next try.

- Alex

[RFC bluetooth-next 2/4] 6lowpan: iphc: add check for reserved values

[Alexander Aring]

This patch adds a check on reserved values for IPHC header. We should at
first check on these fields instead of doing parsing before. Afterwards
we can be sure there are no reserved values anymore. The reserved bits
doesn't contain reserved values for NHC headers. This need to be handled
inside the next layer.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
---
 net/6lowpan/iphc.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c
index 346b5c1..13f5424 100644
--- a/net/6lowpan/iphc.c
+++ b/net/6lowpan/iphc.c
@@ -455,6 +455,20 @@ static const u8 lowpan_ttl_values[] = {
 	[LOWPAN_IPHC_HLIM_11] = 255,
 };
 
+static inline bool lowpan_iphc_is_reserved(u8 iphc1)
+{
+	switch (iphc1 & (LOWPAN_IPHC_DAC | LOWPAN_IPHC_M |
+			 LOWPAN_IPHC_DAM_MASK)) {
+	case LOWPAN_IPHC_DAC | LOWPAN_IPHC_DAM_00:
+	case LOWPAN_IPHC_DAC | LOWPAN_IPHC_M | LOWPAN_IPHC_DAM_01:
+	case LOWPAN_IPHC_DAC | LOWPAN_IPHC_M | LOWPAN_IPHC_DAM_10:
+	case LOWPAN_IPHC_DAC | LOWPAN_IPHC_M | LOWPAN_IPHC_DAM_11:
+		return true;
+	default:
+		return false;
+	}
+}
+
 int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
 			     const void *daddr, const void *saddr)
 {
@@ -466,7 +480,8 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
 		       skb->data, skb->len);
 
 	if (lowpan_fetch_skb(skb, &iphc0, sizeof(iphc0)) ||
-	    lowpan_fetch_skb(skb, &iphc1, sizeof(iphc1)))
+	    lowpan_fetch_skb(skb, &iphc1, sizeof(iphc1)) ||
+	    lowpan_iphc_is_reserved(iphc1))
 		return -EINVAL;
 
 	/* another if the CID flag is set */
-- 
2.6.1

[RFC bluetooth-next 3/4] 6lowpan: iphc: remove handling when dam is zero

[Alexander Aring]

This patch removes handling of LOWPAN_IPHC_DAM_00 inside the
lowpan_compress_addr_64 function. The case of LOWPAN_IPHC_DAM_00 can
never occur. there exists a if branch which use LOWPAN_IPHC_DAM_11 and
LOWPAN_IPHC_DAM_10 and inside the else branch LOWPAN_IPHC_DAM_01. So
LOWPAN_IPHC_DAM_00 can never occur.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
---
 net/6lowpan/iphc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c
index 13f5424..f7f175c 100644
--- a/net/6lowpan/iphc.c
+++ b/net/6lowpan/iphc.c
@@ -594,7 +594,6 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
 EXPORT_SYMBOL_GPL(lowpan_header_decompress);
 
 static const u8 lowpan_iphc_dam_to_sam_value[] = {
-	[LOWPAN_IPHC_DAM_00] = LOWPAN_IPHC_SAM_00,
 	[LOWPAN_IPHC_DAM_01] = LOWPAN_IPHC_SAM_01,
 	[LOWPAN_IPHC_DAM_10] = LOWPAN_IPHC_SAM_10,
 	[LOWPAN_IPHC_DAM_11] = LOWPAN_IPHC_SAM_11,
@@ -603,7 +602,7 @@ static const u8 lowpan_iphc_dam_to_sam_value[] = {
 static u8 lowpan_compress_addr_64(u8 **hc_ptr, const struct in6_addr *ipaddr,
 				  const unsigned char *lladdr, bool sam)
 {
-	u8 dam = LOWPAN_IPHC_DAM_00;
+	u8 dam;
 
 	if (is_addr_mac_addr_based(ipaddr, lladdr)) {
 		dam = LOWPAN_IPHC_DAM_11; /* 0-bits */
-- 
2.6.1

[RFC bluetooth-next 4/4] 6lowpan: iphc: add support for stateful compression

[Alexander Aring]

This patch introduce support for IPHC stateful address compression. It
will offer three debugfs per interface entries, which are:

 - dci_table: destination context indentifier table
 - sci_table: source context indentifier table
 - mcast_sci_table: multicast context identifier table

Example to setup a context id:

A "cat /sys/kernel/debug/6lowpan/lowpan0/dci_table" will display all
contexts which are available. Example:

ID ipv6-address/prefix-length                  state
0  0000:0000:0000:0000:0000:0000:0000:0000/000 0
1  0000:0000:0000:0000:0000:0000:0000:0000/000 0
2  0000:0000:0000:0000:0000:0000:0000:0000/000 0
3  0000:0000:0000:0000:0000:0000:0000:0000/000 0
4  0000:0000:0000:0000:0000:0000:0000:0000/000 0
5  0000:0000:0000:0000:0000:0000:0000:0000/000 0
6  0000:0000:0000:0000:0000:0000:0000:0000/000 0
7  0000:0000:0000:0000:0000:0000:0000:0000/000 0
8  0000:0000:0000:0000:0000:0000:0000:0000/000 0
9  0000:0000:0000:0000:0000:0000:0000:0000/000 0
10 0000:0000:0000:0000:0000:0000:0000:0000/000 0
11 0000:0000:0000:0000:0000:0000:0000:0000/000 0
12 0000:0000:0000:0000:0000:0000:0000:0000/000 0
13 0000:0000:0000:0000:0000:0000:0000:0000/000 0
14 0000:0000:0000:0000:0000:0000:0000:0000/000 0
15 0000:0000:0000:0000:0000:0000:0000:0000/000 0

For setting a context e.g. context id 0, context 2001::, prefix-length
64.

Hint: Simple copy one line and then maniuplate it.

echo "0 2001:0000:0000:0000:0000:0000:0000:0000/64 1" >
/sys/kernel/debug/6lowpan/lowpan0/dci_table

The state will display currently if the context is disabled(0) or
enabled(1).

On transmit side:

The IPHC code will automatically search for a context which would be
match for the address. Then it will be use the context which the
best compression, means the longest prefix which match will be used.

Example:

2001::/126 vs 2001::/127 - the 2001::/127 can be full compressed if the
last bit of the address which has the prefix 2001::/127 is the same like
the IID from the Encapsulating Header. A context ID can also be a
2001::1/128, which is then a full ipv6 address.

On Receive side:

If there is a context defined (when CID not available then it's the
default context 0) then it will be used, if the header doesn't set
SAC or DAC bit thens, it will be dropped.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
---
 include/net/6lowpan.h   |  62 ++++++
 net/6lowpan/6lowpan_i.h |   3 +
 net/6lowpan/core.c      |  17 ++
 net/6lowpan/debugfs.c   | 109 +++++++++-
 net/6lowpan/iphc.c      | 522 ++++++++++++++++++++++++++++++++++++++++++------
 5 files changed, 655 insertions(+), 58 deletions(-)

diff --git a/include/net/6lowpan.h b/include/net/6lowpan.h
index edce9a1..18898db 100644
--- a/include/net/6lowpan.h
+++ b/include/net/6lowpan.h
@@ -73,6 +73,8 @@
 #define LOWPAN_IPHC_MAX_HC_BUF_LEN	(sizeof(struct ipv6hdr) +	\
 					 LOWPAN_IPHC_MAX_HEADER_LEN +	\
 					 LOWPAN_NHC_MAX_HDR_LEN)
+/* SCI/DCI is 4 bit width, so we have maximum 16 entries */
+#define LOWPAN_IPHC_CI_TABLE_SIZE	(1 << 4)
 
 #define LOWPAN_DISPATCH_IPV6		0x41 /* 01000001 = 65 */
 #define LOWPAN_DISPATCH_IPHC		0x60 /* 011xxxxx = ... */
@@ -96,8 +98,44 @@ enum lowpan_lltypes {
 	LOWPAN_LLTYPE_IEEE802154,
 };
 
+enum lowpan_iphc_ctx_states {
+	LOWPAN_IPHC_CTX_STATE_DISABLED,
+	LOWPAN_IPHC_CTX_STATE_ENABLED,
+
+	__LOWPAN_IPHC_CTX_STATE_INVALID,
+	LOWPAN_IPHC_CTX_STATE_MAX = __LOWPAN_IPHC_CTX_STATE_INVALID - 1,
+};
+
+struct lowpan_iphc_ctx {
+	enum lowpan_iphc_ctx_states state;
+	u8 id;
+	struct in6_addr addr;
+	u8 prefix_len;
+};
+
+struct lowpan_iphc_ctx_ops {
+	bool (*valid_prefix)(const struct lowpan_iphc_ctx *ctx);
+	int (*update)(struct lowpan_iphc_ctx *table,
+		      const struct lowpan_iphc_ctx *ctx);
+	struct lowpan_iphc_ctx *(*get_by_id)(const struct net_device *dev,
+					     struct lowpan_iphc_ctx *table,
+					     u8 id);
+	struct lowpan_iphc_ctx *(*get_by_addr)(const struct net_device *dev,
+					       struct lowpan_iphc_ctx *table,
+					       const struct in6_addr *addr);
+};
+
+struct lowpan_iphc_ctx_table {
+	spinlock_t lock;
+	const struct lowpan_iphc_ctx_ops *ops;
+	struct lowpan_iphc_ctx table[LOWPAN_IPHC_CI_TABLE_SIZE];
+};
+
 struct lowpan_priv {
 	enum lowpan_lltypes lltype;
+	struct lowpan_iphc_ctx_table iphc_dci;
+	struct lowpan_iphc_ctx_table iphc_sci;
+	struct lowpan_iphc_ctx_table iphc_mcast_dci;
 
 	/* must be last */
 	u8 priv[0] __aligned(sizeof(void *));
@@ -122,6 +160,30 @@ struct lowpan_802154_cb *lowpan_802154_cb(const struct sk_buff *skb)
 	return (struct lowpan_802154_cb *)skb->cb;
 }
 
+static inline int lowpan_ctx_update(struct lowpan_iphc_ctx_table *t,
+				    const struct lowpan_iphc_ctx *ctx)
+{
+	if (!t->ops->valid_prefix(ctx))
+		return -EINVAL;
+
+	return t->ops->update(t->table, ctx);
+}
+
+static inline struct lowpan_iphc_ctx *
+lowpan_ctx_by_id(const struct net_device *dev, struct lowpan_iphc_ctx_table *t,
+		 u8 id)
+{
+	return t->ops->get_by_id(dev, t->table, id);
+}
+
+static inline struct lowpan_iphc_ctx *
+lowpan_ctx_by_addr(const struct net_device *dev,
+		   struct lowpan_iphc_ctx_table *t,
+		   const struct in6_addr *addr)
+{
+	return t->ops->get_by_addr(dev, t->table, addr);
+}
+
 #ifdef DEBUG
 /* print data in line */
 static inline void raw_dump_inline(const char *caller, char *msg,
diff --git a/net/6lowpan/6lowpan_i.h b/net/6lowpan/6lowpan_i.h
index 102c2a4..531444f 100644
--- a/net/6lowpan/6lowpan_i.h
+++ b/net/6lowpan/6lowpan_i.h
@@ -3,6 +3,9 @@
 
 #include <linux/netdevice.h>
 
+extern const struct lowpan_iphc_ctx_ops iphc_ctx_unicast_ops;
+extern const struct lowpan_iphc_ctx_ops iphc_ctx_mcast_ops;
+
 #ifdef CONFIG_6LOWPAN_DEBUGFS
 int lowpan_dev_debugfs_init(struct net_device *dev);
 
diff --git a/net/6lowpan/core.c b/net/6lowpan/core.c
index 7f46c7e..9e6a0a9 100644
--- a/net/6lowpan/core.c
+++ b/net/6lowpan/core.c
@@ -19,6 +19,8 @@
 
 int lowpan_netdev_setup(struct net_device *dev, enum lowpan_lltypes lltype)
 {
+	int i;
+
 	dev->addr_len = EUI64_ADDR_LEN;
 	dev->type = ARPHRD_6LOWPAN;
 	dev->mtu = IPV6_MIN_MTU;
@@ -26,6 +28,21 @@ int lowpan_netdev_setup(struct net_device *dev, enum lowpan_lltypes lltype)
 
 	lowpan_priv(dev)->lltype = lltype;
 
+	spin_lock_init(&lowpan_priv(dev)->iphc_dci.lock);
+	lowpan_priv(dev)->iphc_dci.ops = &iphc_ctx_unicast_ops;
+
+	spin_lock_init(&lowpan_priv(dev)->iphc_sci.lock);
+	lowpan_priv(dev)->iphc_sci.ops = &iphc_ctx_unicast_ops;
+
+	spin_lock_init(&lowpan_priv(dev)->iphc_mcast_dci.lock);
+	lowpan_priv(dev)->iphc_mcast_dci.ops = &iphc_ctx_mcast_ops;
+
+	for (i = 0; i < LOWPAN_IPHC_CI_TABLE_SIZE; i++) {
+		lowpan_priv(dev)->iphc_dci.table[i].id = i;
+		lowpan_priv(dev)->iphc_sci.table[i].id = i;
+		lowpan_priv(dev)->iphc_mcast_dci.table[i].id = i;
+	}
+
 	return lowpan_dev_debugfs_init(dev);
 }
 EXPORT_SYMBOL(lowpan_netdev_setup);
diff --git a/net/6lowpan/debugfs.c b/net/6lowpan/debugfs.c
index e70eee4..62c5b81 100644
--- a/net/6lowpan/debugfs.c
+++ b/net/6lowpan/debugfs.c
@@ -20,15 +20,122 @@
 
 static struct dentry *lowpan_debugfs;
 
+static int lowpan_context_show(struct seq_file *file, void *offset)
+{
+	struct lowpan_iphc_ctx_table *t = file->private;
+	int i;
+
+	seq_printf(file, "%-2s %-43s %s\n", "ID", "ipv6-address/prefix-length",
+		   "state");
+
+	spin_lock_bh(&t->lock);
+	for (i = 0; i < LOWPAN_IPHC_CI_TABLE_SIZE; i++) {
+		seq_printf(file,
+			   "%-2d %04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x/%03d %d\n",
+			   t->table[i].id,
+			   be16_to_cpu(t->table[i].addr.s6_addr16[0]),
+			   be16_to_cpu(t->table[i].addr.s6_addr16[1]),
+			   be16_to_cpu(t->table[i].addr.s6_addr16[2]),
+			   be16_to_cpu(t->table[i].addr.s6_addr16[3]),
+			   be16_to_cpu(t->table[i].addr.s6_addr16[4]),
+			   be16_to_cpu(t->table[i].addr.s6_addr16[5]),
+			   be16_to_cpu(t->table[i].addr.s6_addr16[6]),
+			   be16_to_cpu(t->table[i].addr.s6_addr16[7]),
+			   t->table[i].prefix_len, t->table[i].state);
+	}
+	spin_unlock_bh(&t->lock);
+
+	return 0;
+}
+
+static int lowpan_context_dbgfs_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, lowpan_context_show, inode->i_private);
+}
+
+static ssize_t lowpan_context_dbgfs_write(struct file *fp,
+					  const char __user *user_buf,
+					  size_t count, loff_t *ppos)
+{
+	char buf[128] = { };
+	struct seq_file *file = fp->private_data;
+	struct lowpan_iphc_ctx_table *t = file->private;
+	struct lowpan_iphc_ctx ctx;
+	int status = count, n, id, state, i, prefix_len, ret;
+	unsigned int addr[8];
+
+	if (copy_from_user(&buf, user_buf, min_t(size_t, sizeof(buf) - 1,
+						 count))) {
+		status = -EFAULT;
+		goto out;
+	}
+
+	n = sscanf(buf, "%d %04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x/%d %d",
+		   &id, &addr[0], &addr[1], &addr[2], &addr[3], &addr[4],
+		   &addr[5], &addr[6], &addr[7], &prefix_len, &state);
+	if (n != 11) {
+		status = -EIO;
+		goto out;
+	}
+
+	if (id > LOWPAN_IPHC_CI_TABLE_SIZE - 1 ||
+	    state > LOWPAN_IPHC_CTX_STATE_MAX || prefix_len > 128) {
+		status = -EINVAL;
+		goto out;
+	}
+
+	ctx.id = id;
+	ctx.state = state;
+	ctx.prefix_len = prefix_len;
+
+	for (i = 0; i < 8; i++)
+		ctx.addr.s6_addr16[i] = cpu_to_be16(addr[i] & 0xffff);
+
+	spin_lock_bh(&t->lock);
+	ret = lowpan_ctx_update(t, &ctx);
+	if (ret < 0)
+		status = ret;
+	spin_unlock_bh(&t->lock);
+
+out:
+	return status;
+}
+
+const struct file_operations lowpan_context_fops = {
+	.open		= lowpan_context_dbgfs_open,
+	.read		= seq_read,
+	.write		= lowpan_context_dbgfs_write,
+	.llseek		= seq_lseek,
+	.release	= single_release,
+};
+
 int lowpan_dev_debugfs_init(struct net_device *dev)
 {
-	static struct dentry *iface;
+	static struct dentry *iface, *dentry;
 
 	/* creating the root */
 	iface = debugfs_create_dir(dev->name, lowpan_debugfs);
 	if (!iface)
 		goto fail;
 
+	dentry = debugfs_create_file("dci_table", 0664, iface,
+				     &lowpan_priv(dev)->iphc_dci,
+				     &lowpan_context_fops);
+	if (!dentry)
+		goto fail;
+
+	dentry = debugfs_create_file("sci_table", 0664, iface,
+				     &lowpan_priv(dev)->iphc_sci,
+				     &lowpan_context_fops);
+	if (!dentry)
+		goto fail;
+
+	dentry = debugfs_create_file("mcast_dci_table", 0664, iface,
+				     &lowpan_priv(dev)->iphc_mcast_dci,
+				     &lowpan_context_fops);
+	if (!dentry)
+		goto fail;
+
 	return 0;
 
 fail:
diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c
index f7f175c..49e59dd 100644
--- a/net/6lowpan/iphc.c
+++ b/net/6lowpan/iphc.c
@@ -56,6 +56,7 @@
 /* special link-layer handling */
 #include <net/mac802154.h>
 
+#include "6lowpan_i.h"
 #include "nhc.h"
 
 /* Values of fields within the IPHC encoding first byte */
@@ -147,6 +148,35 @@
 	 (((a)->s6_addr16[6]) == 0) &&		\
 	 (((a)->s6_addr[14]) == 0))
 
+#define LOWPAN_IPHC_CID_DCI(cid)	(cid & 0x0f)
+#define LOWPAN_IPHC_CID_SCI(cid)	((cid & 0xf0) >> 4)
+
+static inline void *lowpan_iphc_bitcpy(void *dest, const void *src, size_t bits)
+{
+	size_t bytes, remainder;
+	char *_dest = dest;
+	const char *_src = src;
+	u8 remainder_mask = 0x80;
+
+	/* copy bytes */
+	bytes = bits >> 3;
+	memcpy(dest, src, bytes);
+	/* check if we have a rest of the division through 8 */
+	remainder = bits & 0x7;
+	while (remainder) {
+		/* copy last bits beginning from most significant bit */
+		if (_src[bytes] & remainder_mask)
+			_dest[bytes] |= remainder_mask;
+		else
+			_dest[bytes] &= ~remainder_mask;
+
+		remainder_mask >>= 1;
+		remainder--;
+	}
+
+	return dest;
+}
+
 static inline void iphc_uncompress_eui64_lladdr(struct in6_addr *ipaddr,
 						const void *lladdr)
 {
@@ -259,30 +289,59 @@ static int uncompress_addr(struct sk_buff *skb, const struct net_device *dev,
 /* Uncompress address function for source context
  * based address(non-multicast).
  */
-static int uncompress_context_based_src_addr(struct sk_buff *skb,
-					     struct in6_addr *ipaddr,
-					     u8 address_mode)
+static int uncompress_ctx_addr(struct sk_buff *skb,
+			       const struct net_device *dev,
+			       const struct lowpan_iphc_ctx *ctx,
+			       struct in6_addr *ipaddr, u8 address_mode,
+			       const void *lladdr)
 {
+	bool fail;
+
 	switch (address_mode) {
-	case LOWPAN_IPHC_SAM_00:
-		/* unspec address ::
+	/* SAM and DAM are the same here */
+	case LOWPAN_IPHC_DAM_00:
+		fail = false;
+		/* SAM_00 -> unspec address ::
 		 * Do nothing, address is already ::
+		 *
+		 * DAM 00 -> reserved should never occur.
 		 */
 		break;
 	case LOWPAN_IPHC_SAM_01:
-		/* TODO */
+	case LOWPAN_IPHC_DAM_01:
+		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[8], 8);
+		lowpan_iphc_bitcpy(ipaddr, &ctx->addr, ctx->prefix_len);
+		break;
 	case LOWPAN_IPHC_SAM_10:
-		/* TODO */
+	case LOWPAN_IPHC_DAM_10:
+		ipaddr->s6_addr[11] = 0xFF;
+		ipaddr->s6_addr[12] = 0xFE;
+		fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[14], 2);
+		lowpan_iphc_bitcpy(ipaddr, &ctx->addr, ctx->prefix_len);
+		break;
 	case LOWPAN_IPHC_SAM_11:
-		/* TODO */
-		netdev_warn(skb->dev, "SAM value 0x%x not supported\n",
-			    address_mode);
-		return -EINVAL;
+	case LOWPAN_IPHC_DAM_11:
+		fail = false;
+		switch (lowpan_priv(dev)->lltype) {
+		case LOWPAN_LLTYPE_IEEE802154:
+			iphc_uncompress_802154_lladdr(ipaddr, lladdr);
+			break;
+		default:
+			iphc_uncompress_eui64_lladdr(ipaddr, lladdr);
+			break;
+		}
+		lowpan_iphc_bitcpy(ipaddr, &ctx->addr, ctx->prefix_len);
+		break;
 	default:
 		pr_debug("Invalid sam value: 0x%x\n", address_mode);
 		return -EINVAL;
 	}
 
+	if (fail) {
+		pr_debug("Failed to fetch skb data\n");
+		return -EIO;
+	}
+
 	raw_dump_inline(NULL,
 			"Reconstructed context based ipv6 src addr is",
 			ipaddr->s6_addr, 16);
@@ -346,6 +405,29 @@ static int lowpan_uncompress_multicast_daddr(struct sk_buff *skb,
 	return 0;
 }
 
+static int lowpan_uncompress_multicast_ctx_daddr(struct sk_buff *skb,
+						 struct lowpan_iphc_ctx *ctx,
+						 struct in6_addr *ipaddr,
+						 u8 address_mode)
+{
+	bool fail;
+
+	if (address_mode != LOWPAN_IPHC_DAM_00)
+		return -EINVAL;
+
+	ipaddr->s6_addr[0] = 0xFF;
+	fail = lowpan_fetch_skb(skb, &ipaddr->s6_addr[1], 2);
+	fail |= lowpan_fetch_skb(skb, &ipaddr->s6_addr[12], 4);
+	/* take prefix_len and network prefix from the context */
+	ipaddr->s6_addr[3] = ctx->prefix_len;
+	lowpan_iphc_bitcpy(&ipaddr->s6_addr[4], &ctx->addr, ctx->prefix_len);
+
+	if (fail < 0)
+		return -EIO;
+
+	return 0;
+}
+
 /* get the ecn values from iphc tf format and set it to ipv6hdr */
 static inline void lowpan_iphc_tf_set_ecn(struct ipv6hdr *hdr, const u8 *tf)
 {
@@ -473,7 +555,8 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
 			     const void *daddr, const void *saddr)
 {
 	struct ipv6hdr hdr = {};
-	u8 iphc0, iphc1;
+	struct lowpan_iphc_ctx *ci;
+	u8 iphc0, iphc1, cid = 0;
 	int err;
 
 	raw_dump_table(__func__, "raw skb data dump uncompressed",
@@ -484,12 +567,14 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
 	    lowpan_iphc_is_reserved(iphc1))
 		return -EINVAL;
 
-	/* another if the CID flag is set */
-	if (iphc1 & LOWPAN_IPHC_CID)
-		return -ENOTSUPP;
-
 	hdr.version = 6;
 
+	/* default CID = 0, another if the CID flag is set */
+	if (iphc1 & LOWPAN_IPHC_CID) {
+		if (lowpan_fetch_skb(skb, &cid, sizeof(cid)))
+			return -EINVAL;
+	}
+
 	err = lowpan_iphc_tf_decompress(skb, &hdr,
 					iphc0 & LOWPAN_IPHC_TF_MASK);
 	if (err < 0)
@@ -515,10 +600,18 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
 	}
 
 	if (iphc1 & LOWPAN_IPHC_SAC) {
-		/* Source address context based uncompression */
+		spin_lock_bh(&lowpan_priv(dev)->iphc_sci.lock);
+		ci = lowpan_ctx_by_id(dev, &lowpan_priv(dev)->iphc_sci,
+				      LOWPAN_IPHC_CID_SCI(cid));
+		if (!ci) {
+			spin_unlock_bh(&lowpan_priv(dev)->iphc_sci.lock);
+			return -EINVAL;
+		}
+
 		pr_debug("SAC bit is set. Handle context based source address.\n");
-		err = uncompress_context_based_src_addr(skb, &hdr.saddr,
-							iphc1 & LOWPAN_IPHC_SAM_MASK);
+		err = uncompress_ctx_addr(skb, dev, ci, &hdr.saddr,
+					  iphc1 & LOWPAN_IPHC_SAM_MASK, saddr);
+		spin_unlock_bh(&lowpan_priv(dev)->iphc_sci.lock);
 	} else {
 		/* Source address uncompression */
 		pr_debug("source address stateless compression\n");
@@ -530,27 +623,54 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
 	if (err)
 		return -EINVAL;
 
-	/* check for Multicast Compression */
-	if (iphc1 & LOWPAN_IPHC_M) {
-		if (iphc1 & LOWPAN_IPHC_DAC) {
-			pr_debug("dest: context-based mcast compression\n");
-			/* TODO: implement this */
-		} else {
-			err = lowpan_uncompress_multicast_daddr(skb, &hdr.daddr,
-								iphc1 & LOWPAN_IPHC_DAM_MASK);
+	switch (iphc1 & (LOWPAN_IPHC_M | LOWPAN_IPHC_DAC)) {
+	case LOWPAN_IPHC_M | LOWPAN_IPHC_DAC:
+		spin_lock_bh(&lowpan_priv(dev)->iphc_mcast_dci.lock);
+		ci = lowpan_ctx_by_id(dev, &lowpan_priv(dev)->iphc_mcast_dci,
+				      LOWPAN_IPHC_CID_DCI(cid));
+		if (!ci) {
+			spin_unlock_bh(&lowpan_priv(dev)->iphc_mcast_dci.lock);
+			return -EINVAL;
+		}
 
-			if (err)
-				return -EINVAL;
+		/* multicast with context */
+		pr_debug("dest: context-based mcast compression\n");
+		err = lowpan_uncompress_multicast_ctx_daddr(skb, ci,
+							    &hdr.daddr,
+							    iphc1 & LOWPAN_IPHC_DAM_MASK);
+		spin_unlock_bh(&lowpan_priv(dev)->iphc_mcast_dci.lock);
+		break;
+	case LOWPAN_IPHC_M:
+		/* multicast */
+		err = lowpan_uncompress_multicast_daddr(skb, &hdr.daddr,
+							iphc1 & LOWPAN_IPHC_DAM_MASK);
+		break;
+	case LOWPAN_IPHC_DAC:
+		spin_lock_bh(&lowpan_priv(dev)->iphc_dci.lock);
+		ci = lowpan_ctx_by_id(dev, &lowpan_priv(dev)->iphc_dci,
+				      LOWPAN_IPHC_CID_DCI(cid));
+		if (!ci) {
+			spin_unlock_bh(&lowpan_priv(dev)->iphc_dci.lock);
+			return -EINVAL;
 		}
-	} else {
+
+		/* Destination address context based uncompression */
+		pr_debug("DAC bit is set. Handle context based destination address.\n");
+		err = uncompress_ctx_addr(skb, dev, ci, &hdr.daddr,
+					  iphc1 & LOWPAN_IPHC_DAM_MASK, daddr);
+		spin_unlock_bh(&lowpan_priv(dev)->iphc_dci.lock);
+		break;
+	default:
 		err = uncompress_addr(skb, dev, &hdr.daddr,
 				      iphc1 & LOWPAN_IPHC_DAM_MASK, daddr);
 		pr_debug("dest: stateless compression mode %d dest %pI6c\n",
 			 iphc1 & LOWPAN_IPHC_DAM_MASK, &hdr.daddr);
-		if (err)
-			return -EINVAL;
+		break;
 	}
 
+	if (err)
+		return -EINVAL;
+
 	/* Next header data uncompression */
 	if (iphc0 & LOWPAN_IPHC_NH) {
 		err = lowpan_nhc_do_uncompression(skb, dev, &hdr);
@@ -599,6 +719,60 @@ static const u8 lowpan_iphc_dam_to_sam_value[] = {
 	[LOWPAN_IPHC_DAM_11] = LOWPAN_IPHC_SAM_11,
 };
 
+static u8 lowpan_compress_ctx_addr(u8 **hc_ptr, const struct in6_addr *ipaddr,
+				   const struct lowpan_iphc_ctx *ctx,
+				   const unsigned char *lladdr, bool sam)
+{
+	struct in6_addr tmp = {};
+	u8 dam;
+
+	/* check for SAM/DAM = 11 */
+	memcpy(&tmp.s6_addr[8], lladdr, 8);
+	/* second bit-flip (Universe/Local)
+	 * is done according RFC2464
+	 */
+	tmp.s6_addr[8] ^= 0x02;
+	/* context information are always used */
+	lowpan_iphc_bitcpy(&tmp, &ctx->addr, ctx->prefix_len);
+	if (ipv6_addr_equal(&tmp, ipaddr)) {
+		dam = LOWPAN_IPHC_DAM_11;
+		goto out;
+	}
+
+	memset(&tmp, 0, sizeof(tmp));
+	/* check for SAM/DAM = 01 */
+	tmp.s6_addr[11] = 0xFF;
+	tmp.s6_addr[12] = 0xFE;
+	memcpy(&tmp.s6_addr[14], &ipaddr->s6_addr[14], 2);
+	/* context information are always used */
+	lowpan_iphc_bitcpy(&tmp, &ctx->addr, ctx->prefix_len);
+	if (ipv6_addr_equal(&tmp, ipaddr)) {
+		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr[14], 2);
+		dam = LOWPAN_IPHC_DAM_10;
+		goto out;
+	}
+
+	memset(&tmp, 0, sizeof(tmp));
+	/* check for SAM/DAM = 10, should always match */
+	memcpy(&tmp.s6_addr[8], &ipaddr->s6_addr[8], 8);
+	/* context information are always used */
+	lowpan_iphc_bitcpy(&tmp, &ctx->addr, ctx->prefix_len);
+	if (ipv6_addr_equal(&tmp, ipaddr)) {
+		lowpan_push_hc_data(hc_ptr, &ipaddr->s6_addr[8], 8);
+		dam = LOWPAN_IPHC_DAM_01;
+		goto out;
+	}
+
+	WARN_ON_ONCE("context found but no address mode matched\n");
+	return -EINVAL;
+out:
+
+	if (sam)
+		return lowpan_iphc_dam_to_sam_value[dam];
+	else
+		return dam;
+}
+
 static u8 lowpan_compress_addr_64(u8 **hc_ptr, const struct in6_addr *ipaddr,
 				  const unsigned char *lladdr, bool sam)
 {
@@ -722,6 +896,21 @@ static u8 lowpan_iphc_tf_compress(u8 **hc_ptr, const struct ipv6hdr *hdr)
 	return val;
 }
 
+static u8 lowpan_iphc_mcast_ctx_addr_compress(u8 **hc_ptr,
+					      const struct lowpan_iphc_ctx *ctx,
+					      const struct in6_addr *ipaddr)
+{
+	u8 data[6];
+
+	/* flags/scope, reserved (RIID) */
+	memcpy(data, &ipaddr->s6_addr[1], 2);
+	/* group ID */
+	memcpy(&data[1], &ipaddr->s6_addr[11], 4);
+	lowpan_push_hc_data(hc_ptr, data, 6);
+
+	return LOWPAN_IPHC_DAM_00;
+}
+
 static u8 lowpan_iphc_mcast_addr_compress(u8 **hc_ptr,
 					  const struct in6_addr *ipaddr)
 {
@@ -756,10 +945,11 @@ static u8 lowpan_iphc_mcast_addr_compress(u8 **hc_ptr,
 int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
 			   const void *daddr, const void *saddr)
 {
-	u8 iphc0, iphc1, *hc_ptr;
+	u8 iphc0, iphc1, *hc_ptr, cid = 0;
 	struct ipv6hdr *hdr;
 	u8 head[LOWPAN_IPHC_MAX_HC_BUF_LEN] = {};
-	int ret, addr_type;
+	struct lowpan_iphc_ctx *dci, *sci, dci_entry, sci_entry;
+	int ret, ipv6_daddr_type, ipv6_saddr_type;
 
 	if (skb->protocol != htons(ETH_P_IPV6))
 		return -EINVAL;
@@ -783,14 +973,47 @@ int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
 	iphc0 = LOWPAN_DISPATCH_IPHC;
 	iphc1 = 0;
 
-	/* TODO: context lookup */
-
 	raw_dump_inline(__func__, "saddr", saddr, EUI64_ADDR_LEN);
 	raw_dump_inline(__func__, "daddr", daddr, EUI64_ADDR_LEN);
 
 	raw_dump_table(__func__, "sending raw skb network uncompressed packet",
 		       skb->data, skb->len);
 
+	ipv6_daddr_type = ipv6_addr_type(&hdr->daddr);
+	if (ipv6_daddr_type & IPV6_ADDR_MULTICAST) {
+		spin_lock_bh(&lowpan_priv(dev)->iphc_mcast_dci.lock);
+		dci = lowpan_ctx_by_addr(dev, &lowpan_priv(dev)->iphc_mcast_dci,
+					 &hdr->daddr);
+		if (dci) {
+			memcpy(&dci_entry, dci, sizeof(*dci));
+			cid |= dci->id;
+		}
+		spin_unlock_bh(&lowpan_priv(dev)->iphc_mcast_dci.lock);
+	} else {
+		spin_lock_bh(&lowpan_priv(dev)->iphc_dci.lock);
+		dci = lowpan_ctx_by_addr(dev, &lowpan_priv(dev)->iphc_dci,
+					 &hdr->daddr);
+		if (dci) {
+			memcpy(&dci_entry, dci, sizeof(*dci));
+			cid |= dci->id;
+		}
+		spin_unlock_bh(&lowpan_priv(dev)->iphc_dci.lock);
+	}
+
+	spin_lock_bh(&lowpan_priv(dev)->iphc_sci.lock);
+	sci = lowpan_ctx_by_addr(dev, &lowpan_priv(dev)->iphc_sci,
+				 &hdr->saddr);
+	if (sci) {
+		memcpy(&sci_entry, sci, sizeof(*sci));
+		cid |= (sci->id << 4);
+	}
+	spin_unlock_bh(&lowpan_priv(dev)->iphc_sci.lock);
+
+	if (sci || dci) {
+		iphc1 |= LOWPAN_IPHC_CID;
+		lowpan_push_hc_data(&hc_ptr, &cid, sizeof(cid));
+	}
+
 	/* Traffic Class, Flow Label compression */
 	iphc0 |= lowpan_iphc_tf_compress(&hc_ptr, hdr);
 
@@ -827,39 +1050,63 @@ int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
 				    sizeof(hdr->hop_limit));
 	}
 
-	addr_type = ipv6_addr_type(&hdr->saddr);
+	ipv6_saddr_type = ipv6_addr_type(&hdr->saddr);
 	/* source address compression */
-	if (addr_type == IPV6_ADDR_ANY) {
+	if (ipv6_saddr_type == IPV6_ADDR_ANY) {
 		pr_debug("source address is unspecified, setting SAC\n");
 		iphc1 |= LOWPAN_IPHC_SAC;
 	} else {
-		if (addr_type & IPV6_ADDR_LINKLOCAL) {
-			iphc1 |= lowpan_compress_addr_64(&hc_ptr, &hdr->saddr,
-							 saddr, true);
-			pr_debug("source address unicast link-local %pI6c iphc1 0x%02x\n",
-				 &hdr->saddr, iphc1);
+		if (sci) {
+			iphc1 |= lowpan_compress_ctx_addr(&hc_ptr, &hdr->saddr,
+							  &sci_entry, saddr,
+							  true);
+			iphc1 |= LOWPAN_IPHC_SAC;
 		} else {
-			pr_debug("send the full source address\n");
-			lowpan_push_hc_data(&hc_ptr, hdr->saddr.s6_addr, 16);
+			if (ipv6_saddr_type & IPV6_ADDR_LINKLOCAL) {
+				iphc1 |= lowpan_compress_addr_64(&hc_ptr,
+								 &hdr->saddr,
+								 saddr, true);
+				pr_debug("source address unicast link-local %pI6c iphc1 0x%02x\n",
+					 &hdr->saddr, iphc1);
+			} else {
+				pr_debug("send the full source address\n");
+				lowpan_push_hc_data(&hc_ptr,
+						    hdr->saddr.s6_addr, 16);
+			}
 		}
 	}
 
-	addr_type = ipv6_addr_type(&hdr->daddr);
 	/* destination address compression */
-	if (addr_type & IPV6_ADDR_MULTICAST) {
+	if (ipv6_daddr_type & IPV6_ADDR_MULTICAST) {
 		pr_debug("destination address is multicast: ");
-		iphc1 |= LOWPAN_IPHC_M;
-		iphc1 |= lowpan_iphc_mcast_addr_compress(&hc_ptr, &hdr->daddr);
+		if (dci) {
+			iphc1 |= lowpan_iphc_mcast_ctx_addr_compress(&hc_ptr,
+								     &dci_entry,
+								     &hdr->daddr);
+		} else {
+			iphc1 |= LOWPAN_IPHC_M;
+			iphc1 |= lowpan_iphc_mcast_addr_compress(&hc_ptr,
+								 &hdr->daddr);
+		}
 	} else {
-		if (addr_type & IPV6_ADDR_LINKLOCAL) {
-			/* TODO: context lookup */
-			iphc1 |= lowpan_compress_addr_64(&hc_ptr, &hdr->daddr,
-							 daddr, false);
-			pr_debug("dest address unicast link-local %pI6c "
-				 "iphc1 0x%02x\n", &hdr->daddr, iphc1);
+		if (dci) {
+			iphc1 |= lowpan_compress_ctx_addr(&hc_ptr, &hdr->daddr,
+							  &dci_entry, daddr,
+							  false);
+			iphc1 |= LOWPAN_IPHC_DAC;
 		} else {
-			pr_debug("dest address unicast %pI6c\n", &hdr->daddr);
-			lowpan_push_hc_data(&hc_ptr, hdr->daddr.s6_addr, 16);
+			if (ipv6_daddr_type & IPV6_ADDR_LINKLOCAL) {
+				iphc1 |= lowpan_compress_addr_64(&hc_ptr,
+								 &hdr->daddr,
+								 daddr, false);
+				pr_debug("dest address unicast link-local %pI6c iphc1 0x%02x\n",
+					 &hdr->daddr, iphc1);
+			} else {
+				pr_debug("dest address unicast %pI6c\n",
+					 &hdr->daddr);
+				lowpan_push_hc_data(&hc_ptr,
+						    hdr->daddr.s6_addr, 16);
+			}
 		}
 	}
 
@@ -885,3 +1132,164 @@ int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
 	return 0;
 }
 EXPORT_SYMBOL_GPL(lowpan_header_compress);
+
+static bool lowpan_iphc_ctx_valid_prefix(const struct lowpan_iphc_ctx *ctx)
+{
+	/* prefix which are smaller than 64 bits are not valid, users
+	 * may mean than a prefix which is filled with zero until 64th bit.
+	 * Refere rfc6282 "Any remaining bits are zero." The remaining bits
+	 * in this case where are the prefix(< 64) ends until IID starts.
+	 */
+	if (ctx->prefix_len < 64)
+		return false;
+
+	return true;
+}
+
+static bool
+lowpan_iphc_mcast_ctx_valid_prefix(const struct lowpan_iphc_ctx *ctx)
+{
+	/* network prefix for multicast is at maximum 64 bits long */
+	if (ctx->prefix_len > 64)
+		return false;
+
+	return true;
+}
+
+static int lowpan_iphc_ctx_update(struct lowpan_iphc_ctx *table,
+				  const struct lowpan_iphc_ctx *ctx)
+{
+	int ret = 0, i;
+
+	switch (ctx->state) {
+	case LOWPAN_IPHC_CTX_STATE_DISABLED:
+		/* we don't care about if disabled */
+		break;
+	case LOWPAN_IPHC_CTX_STATE_ENABLED:
+		for (i = 0; i < LOWPAN_IPHC_CI_TABLE_SIZE; i++) {
+			if (ctx->prefix_len != table[i].prefix_len)
+				continue;
+
+			if (ipv6_prefix_equal(&ctx->addr, &table[i].addr,
+					      ctx->prefix_len)) {
+				switch (table[i].state) {
+				case LOWPAN_IPHC_CTX_STATE_ENABLED:
+					ret = -EEXIST;
+					goto out;
+				default:
+					break;
+				}
+			}
+		}
+		break;
+	default:
+		break;
+	}
+
+	memcpy(&table[ctx->id], ctx, sizeof(*ctx));
+
+out:
+	return ret;
+}
+
+static struct lowpan_iphc_ctx *
+lowpan_iphc_ctx_get_by_id(const struct net_device *dev,
+			  struct lowpan_iphc_ctx *table, u8 id)
+{
+	struct lowpan_iphc_ctx *ret = NULL;
+
+	WARN_ON_ONCE(id > LOWPAN_IPHC_CI_TABLE_SIZE);
+
+	switch (table[id].state) {
+	case LOWPAN_IPHC_CTX_STATE_ENABLED:
+		ret = &table[id];
+		break;
+	default:
+		break;
+	}
+
+	return ret;
+}
+
+static struct lowpan_iphc_ctx *
+lowpan_iphc_ctx_get_by_addr(const struct net_device *dev,
+			    struct lowpan_iphc_ctx *table,
+			    const struct in6_addr *addr)
+{
+	struct lowpan_iphc_ctx *ret = NULL;
+	struct in6_addr addr_prefix;
+	int i;
+
+	for (i = 0; i < LOWPAN_IPHC_CI_TABLE_SIZE; i++) {
+		ipv6_addr_prefix(&addr_prefix, addr, table[i].prefix_len);
+
+		if (ipv6_prefix_equal(&addr_prefix, &table[i].addr,
+				      table[i].prefix_len)) {
+			switch (table[i].state) {
+			case LOWPAN_IPHC_CTX_STATE_ENABLED:
+				/* remember first match */
+				if (!ret) {
+					ret = &table[i];
+					continue;
+				}
+
+				/* get the context with longest prefix_len */
+				if (table[i].prefix_len > ret->prefix_len)
+					ret = &table[i];
+				break;
+			default:
+				break;
+			}
+		}
+	}
+
+	return ret;
+}
+
+static struct lowpan_iphc_ctx *
+lowpan_iphc_ctx_get_by_mcast_addr(const struct net_device *dev,
+				  struct lowpan_iphc_ctx *table,
+				  const struct in6_addr *addr)
+{
+	struct lowpan_iphc_ctx *ret = NULL;
+	struct in6_addr addr_mcast;
+	int i;
+
+	/* init mcast address with  */
+	memcpy(&addr_mcast, addr, sizeof(*addr));
+
+	for (i = 0; i < LOWPAN_IPHC_CI_TABLE_SIZE; i++) {
+		/* setting plen */
+		addr_mcast.s6_addr[3] = table[i].prefix_len;
+		/* zero network prefix */
+		memset(&addr_mcast.s6_addr[4], 0, 8);
+		/* setting network prefix (bits) */
+		lowpan_iphc_bitcpy(&addr_mcast.s6_addr[4], &table[i].addr,
+				   table[i].prefix_len);
+
+		if (ipv6_addr_equal(addr, &addr_mcast)) {
+			switch (table[i].state) {
+			case LOWPAN_IPHC_CTX_STATE_ENABLED:
+				return &table[i];
+			default:
+				break;
+			}
+		}
+	}
+
+	return ret;
+}
+
+const struct lowpan_iphc_ctx_ops iphc_ctx_unicast_ops = {
+	.valid_prefix = lowpan_iphc_ctx_valid_prefix,
+	.update = lowpan_iphc_ctx_update,
+	.get_by_id = lowpan_iphc_ctx_get_by_id,
+	.get_by_addr = lowpan_iphc_ctx_get_by_addr,
+};
+
+const struct lowpan_iphc_ctx_ops iphc_ctx_mcast_ops = {
+	.valid_prefix = lowpan_iphc_mcast_ctx_valid_prefix,
+	.update = lowpan_iphc_ctx_update,
+	.get_by_id = lowpan_iphc_ctx_get_by_id,
+	.get_by_addr = lowpan_iphc_ctx_get_by_mcast_addr,
+};
-- 
2.6.1

Re: [RFC bluetooth-next 4/4] 6lowpan: iphc: add support for stateful compression

[Michael Richardson]

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These patches are very nice to have, I will attempt to test them out.
I am waiting for a JTAG programmer to unwedge my openmote, and then I'll
put RIOT on that, but in the meantime I'll be testing against Contiki
on Econotag.

One thing that I wanted to add was a counter per type of HC header decoded.
I seemed to recall that the was some RCU-ish way to do lock-less 64-bit
counters, but I haven't tracked down the right reference.


--
]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        | network architect  [
]     mcr@sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [


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Re: [RFC bluetooth-next 4/4] 6lowpan: iphc: add support for stateful compression

[Alexander Aring]

Hi Michael,

On Fri, Nov 13, 2015 at 01:08:02PM -0500, Michael Richardson wrote:
> 
> These patches are very nice to have, I will attempt to test them out.
> I am waiting for a JTAG programmer to unwedge my openmote, and then I'll
> put RIOT on that, but in the meantime I'll be testing against Contiki
> on Econotag.
> 

ok, thanks.

> One thing that I wanted to add was a counter per type of HC header decoded.
> I seemed to recall that the was some RCU-ish way to do lock-less 64-bit
> counters, but I haven't tracked down the right reference.
> 

Do you want to have this per interface or overall? We could make both.
For the lock-less part a per-cpu counter would be fit here, it will
summarize then all counters per-cpu if they will be requested.

- Alex