6lowpan: rework tc and flow label handling
This patch reworks the handling of compression/decompression of traffic class and flow label handling. The current method is hard to understand, also doesn't checks if we can read the buffer from skb length. I tried to put the shifting operations into static inline functions and comment each steps which I did there to make it hopefully somewhat more readable. The big mess to deal with that is the that the ipv6 header bring the order "DSCP + ECN" but iphc uses "ECN + DSCP". Additional the DCSP + ECN bits are splitted in ipv6_hdr inside the priority and flow_lbl[0] fields. I tested these compressions by using fakelb 802.15.4 driver and manipulate the tc and flow label fields manually in function "__ip6_local_out" before the skb will be send to lower layers. Then I looked up the tc and flow label fields in wireshark on a wpan and lowpan interface. Signed-off-by: Alexander Aring <alex.aring@gmail.com> Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
This commit is contained in:
Alexander Aring
Marcel Holtmann
parent
c8a3e7eb98
commit
b5af9bdbfe
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@ -346,6 +346,108 @@ static int lowpan_uncompress_multicast_daddr(struct sk_buff *skb,
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return 0;
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}
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/* get the ecn values from iphc tf format and set it to ipv6hdr */
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static inline void lowpan_iphc_tf_set_ecn(struct ipv6hdr *hdr, const u8 *tf)
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{
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/* get the two higher bits which is ecn */
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u8 ecn = tf[0] & 0xc0;
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/* ECN takes 0x30 in hdr->flow_lbl[0] */
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hdr->flow_lbl[0] |= (ecn >> 2);
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}
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/* get the dscp values from iphc tf format and set it to ipv6hdr */
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static inline void lowpan_iphc_tf_set_dscp(struct ipv6hdr *hdr, const u8 *tf)
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{
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/* DSCP is at place after ECN */
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u8 dscp = tf[0] & 0x3f;
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/* The four highest bits need to be set at hdr->priority */
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hdr->priority |= ((dscp & 0x3c) >> 2);
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/* The two lower bits is part of hdr->flow_lbl[0] */
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hdr->flow_lbl[0] |= ((dscp & 0x03) << 6);
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}
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/* get the flow label values from iphc tf format and set it to ipv6hdr */
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static inline void lowpan_iphc_tf_set_lbl(struct ipv6hdr *hdr, const u8 *lbl)
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{
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/* flow label is always some array started with lower nibble of
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* flow_lbl[0] and followed with two bytes afterwards. Inside inline
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* data the flow_lbl position can be different, which will be handled
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* by lbl pointer. E.g. case "01" vs "00" the traffic class is 8 bit
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* shifted, the different lbl pointer will handle that.
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*
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* The flow label will started at lower nibble of flow_lbl[0], the
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* higher nibbles are part of DSCP + ECN.
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*/
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hdr->flow_lbl[0] |= lbl[0] & 0x0f;
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memcpy(&hdr->flow_lbl[1], &lbl[1], 2);
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}
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/* lowpan_iphc_tf_decompress - decompress the traffic class.
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* This function will return zero on success, a value lower than zero if
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* failed.
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*/
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static int lowpan_iphc_tf_decompress(struct sk_buff *skb, struct ipv6hdr *hdr,
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u8 val)
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{
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u8 tf[4];
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/* Traffic Class and Flow Label */
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switch (val) {
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case LOWPAN_IPHC_TF_00:
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/* ECN + DSCP + 4-bit Pad + Flow Label (4 bytes) */
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if (lowpan_fetch_skb(skb, tf, 4))
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return -EINVAL;
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/* 1 2 3
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* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* |ECN| DSCP | rsv | Flow Label |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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lowpan_iphc_tf_set_ecn(hdr, tf);
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lowpan_iphc_tf_set_dscp(hdr, tf);
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lowpan_iphc_tf_set_lbl(hdr, &tf[1]);
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break;
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case LOWPAN_IPHC_TF_01:
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/* ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided. */
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if (lowpan_fetch_skb(skb, tf, 3))
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return -EINVAL;
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/* 1 2
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* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* |ECN|rsv| Flow Label |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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lowpan_iphc_tf_set_ecn(hdr, tf);
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lowpan_iphc_tf_set_lbl(hdr, &tf[0]);
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break;
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case LOWPAN_IPHC_TF_10:
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/* ECN + DSCP (1 byte), Flow Label is elided. */
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if (lowpan_fetch_skb(skb, tf, 1))
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return -EINVAL;
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/* 0 1 2 3 4 5 6 7
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* +-+-+-+-+-+-+-+-+
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* |ECN| DSCP |
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* +-+-+-+-+-+-+-+-+
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*/
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lowpan_iphc_tf_set_ecn(hdr, tf);
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lowpan_iphc_tf_set_dscp(hdr, tf);
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break;
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case LOWPAN_IPHC_TF_11:
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/* Traffic Class and Flow Label are elided */
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break;
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default:
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WARN_ON_ONCE(1);
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return -EINVAL;
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}
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return 0;
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}
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/* TTL uncompression values */
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static const u8 lowpan_ttl_values[] = {
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[LOWPAN_IPHC_HLIM_01] = 1,
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@ -357,7 +459,7 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
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const void *daddr, const void *saddr)
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{
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struct ipv6hdr hdr = {};
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u8 iphc0, iphc1, tmp = 0;
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u8 iphc0, iphc1;
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int err;
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raw_dump_table(__func__, "raw skb data dump uncompressed",
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@ -373,49 +475,10 @@ int lowpan_header_decompress(struct sk_buff *skb, const struct net_device *dev,
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hdr.version = 6;
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/* Traffic Class and Flow Label */
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switch (iphc0 & LOWPAN_IPHC_TF_MASK) {
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/* Traffic Class and FLow Label carried in-line
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* ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
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*/
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case LOWPAN_IPHC_TF_00:
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if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
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return -EINVAL;
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memcpy(&hdr.flow_lbl, &skb->data[0], 3);
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skb_pull(skb, 3);
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hdr.priority = ((tmp >> 2) & 0x0f);
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hdr.flow_lbl[0] = ((tmp >> 2) & 0x30) | (tmp << 6) |
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(hdr.flow_lbl[0] & 0x0f);
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break;
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/* Flow Label carried in-line
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* ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
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*/
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case LOWPAN_IPHC_TF_01:
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if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
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return -EINVAL;
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hdr.flow_lbl[0] = (tmp & 0x0F) | ((tmp >> 2) & 0x30);
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memcpy(&hdr.flow_lbl[1], &skb->data[0], 2);
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skb_pull(skb, 2);
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break;
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/* Traffic class carried in-line
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* ECN + DSCP (1 byte), Flow Label is elided
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*/
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case LOWPAN_IPHC_TF_10:
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if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
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return -EINVAL;
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hdr.priority = ((tmp >> 2) & 0x0f);
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hdr.flow_lbl[0] = ((tmp << 6) & 0xC0) | ((tmp >> 2) & 0x30);
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break;
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/* Traffic Class and Flow Label are elided */
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case LOWPAN_IPHC_TF_11:
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break;
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default:
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WARN_ON_ONCE(1);
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break;
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}
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err = lowpan_iphc_tf_decompress(skb, &hdr,
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iphc0 & LOWPAN_IPHC_TF_MASK);
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if (err < 0)
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return err;
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/* Next Header */
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if (!(iphc0 & LOWPAN_IPHC_NH)) {
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@ -550,10 +613,105 @@ static u8 lowpan_compress_addr_64(u8 **hc_ptr, const struct in6_addr *ipaddr,
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return dam;
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}
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/* lowpan_iphc_get_tc - get the ECN + DCSP fields in hc format */
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static inline u8 lowpan_iphc_get_tc(const struct ipv6hdr *hdr)
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{
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u8 dscp, ecn;
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/* hdr->priority contains the higher bits of dscp, lower are part of
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* flow_lbl[0]. Note ECN, DCSP is swapped in ipv6 hdr.
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*/
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dscp = (hdr->priority << 2) | ((hdr->flow_lbl[0] & 0xc0) >> 6);
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/* ECN is at the two lower bits from first nibble of flow_lbl[0] */
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ecn = (hdr->flow_lbl[0] & 0x30);
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/* for pretty debug output, also shift ecn to get the ecn value */
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pr_debug("ecn 0x%02x dscp 0x%02x\n", ecn >> 4, dscp);
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/* ECN is at 0x30 now, shift it to have ECN + DCSP */
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return (ecn << 2) | dscp;
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}
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/* lowpan_iphc_is_flow_lbl_zero - check if flow label is zero */
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static inline bool lowpan_iphc_is_flow_lbl_zero(const struct ipv6hdr *hdr)
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{
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return ((!(hdr->flow_lbl[0] & 0x0f)) &&
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!hdr->flow_lbl[1] && !hdr->flow_lbl[2]);
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}
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/* lowpan_iphc_tf_compress - compress the traffic class which is set by
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* ipv6hdr. Return the corresponding format identifier which is used.
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*/
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static u8 lowpan_iphc_tf_compress(u8 **hc_ptr, const struct ipv6hdr *hdr)
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{
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/* get ecn dscp data in a byteformat as: ECN(hi) + DSCP(lo) */
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u8 tc = lowpan_iphc_get_tc(hdr), tf[4], val;
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/* printout the traffic class in hc format */
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pr_debug("tc 0x%02x\n", tc);
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if (lowpan_iphc_is_flow_lbl_zero(hdr)) {
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if (!tc) {
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/* 11: Traffic Class and Flow Label are elided. */
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val = LOWPAN_IPHC_TF_11;
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} else {
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/* 10: ECN + DSCP (1 byte), Flow Label is elided.
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*
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* 0 1 2 3 4 5 6 7
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* +-+-+-+-+-+-+-+-+
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* |ECN| DSCP |
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* +-+-+-+-+-+-+-+-+
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*/
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lowpan_push_hc_data(hc_ptr, &tc, sizeof(tc));
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val = LOWPAN_IPHC_TF_10;
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}
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} else {
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/* check if dscp is zero, it's after the first two bit */
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if (!(tc & 0x3f)) {
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/* 01: ECN + 2-bit Pad + Flow Label (3 bytes), DSCP is elided
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*
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* 1 2
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* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* |ECN|rsv| Flow Label |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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memcpy(&tf[0], &hdr->flow_lbl[0], 3);
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/* zero the highest 4-bits, contains DCSP + ECN */
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tf[0] &= ~0xf0;
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/* set ECN */
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tf[0] |= (tc & 0xc0);
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lowpan_push_hc_data(hc_ptr, tf, 3);
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val = LOWPAN_IPHC_TF_01;
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} else {
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/* 00: ECN + DSCP + 4-bit Pad + Flow Label (4 bytes)
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*
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* 1 2 3
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* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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* |ECN| DSCP | rsv | Flow Label |
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* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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*/
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memcpy(&tf[0], &tc, sizeof(tc));
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/* highest nibble of flow_lbl[0] is part of DSCP + ECN
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* which will be the 4-bit pad and will be filled with
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* zeros afterwards.
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*/
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memcpy(&tf[1], &hdr->flow_lbl[0], 3);
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/* zero the 4-bit pad, which is reserved */
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tf[1] &= ~0xf0;
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lowpan_push_hc_data(hc_ptr, tf, 4);
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val = LOWPAN_IPHC_TF_00;
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}
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}
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return val;
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}
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int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
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const void *daddr, const void *saddr)
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{
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u8 tmp, iphc0, iphc1, *hc_ptr;
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u8 iphc0, iphc1, *hc_ptr;
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struct ipv6hdr *hdr;
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u8 head[LOWPAN_IPHC_MAX_HC_BUF_LEN] = {};
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int ret, addr_type;
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@ -588,46 +746,8 @@ int lowpan_header_compress(struct sk_buff *skb, const struct net_device *dev,
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raw_dump_table(__func__, "sending raw skb network uncompressed packet",
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skb->data, skb->len);
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/* Traffic class, flow label
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* If flow label is 0, compress it. If traffic class is 0, compress it
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* We have to process both in the same time as the offset of traffic
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* class depends on the presence of version and flow label
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*/
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/* hc format of TC is ECN | DSCP , original one is DSCP | ECN */
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tmp = (hdr->priority << 4) | (hdr->flow_lbl[0] >> 4);
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tmp = ((tmp & 0x03) << 6) | (tmp >> 2);
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if (((hdr->flow_lbl[0] & 0x0F) == 0) &&
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(hdr->flow_lbl[1] == 0) && (hdr->flow_lbl[2] == 0)) {
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/* flow label can be compressed */
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iphc0 |= LOWPAN_IPHC_TF_10;
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if ((hdr->priority == 0) &&
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((hdr->flow_lbl[0] & 0xF0) == 0)) {
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/* compress (elide) all */
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iphc0 |= LOWPAN_IPHC_TF_11;
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} else {
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/* compress only the flow label */
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*hc_ptr = tmp;
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hc_ptr += 1;
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}
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} else {
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/* Flow label cannot be compressed */
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if ((hdr->priority == 0) &&
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((hdr->flow_lbl[0] & 0xF0) == 0)) {
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/* compress only traffic class */
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iphc0 |= LOWPAN_IPHC_TF_01;
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*hc_ptr = (tmp & 0xc0) | (hdr->flow_lbl[0] & 0x0F);
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memcpy(hc_ptr + 1, &hdr->flow_lbl[1], 2);
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hc_ptr += 3;
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} else {
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/* compress nothing */
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memcpy(hc_ptr, hdr, 4);
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/* replace the top byte with new ECN | DSCP format */
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*hc_ptr = tmp;
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hc_ptr += 4;
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}
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}
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/* Traffic Class, Flow Label compression */
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iphc0 |= lowpan_iphc_tf_compress(&hc_ptr, hdr);
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/* NOTE: payload length is always compressed */
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