Hello everybody, below is the patch which adds support for fragmentation in 6LoWPAN point to point networks. This activity needs because of difference in MTU: 1280 ipv6 and 128 ieee802.15.4 This patch is just a draft. Could anyone please look at it and let me know your opinion. The most doubtful moments for me are: 1. Should the list 'frag_list' and the mutex 'flist_lock' be included into dev private data? 2. Can I use 'dev_queue_xmit' to send fragments to queue? 3. Creating new 'skb' instead of copying and modifying main one. With best regards, Alexander
>From 48472bae269b7b1a4047967ec21eadb217c4fd6d Mon Sep 17 00:00:00 2001 From: Alexander Smirnov <alex.bluesman.smirnov@xxxxxxxxx> Date: Thu, 20 Oct 2011 15:02:36 +0400 Subject: [PATCH] 6LoWPAN fragmentation support Signed-off-by: Alexander Smirnov <alex.bluesman.smirnov@xxxxxxxxx> --- net/ieee802154/6lowpan.c | 286 +++++++++++++++++++++++++++++++++++++++++++++- net/ieee802154/6lowpan.h | 3 + 2 files changed, 288 insertions(+), 1 deletions(-) diff --git a/net/ieee802154/6lowpan.c b/net/ieee802154/6lowpan.c index 96877bd..1923ec7 100644 --- a/net/ieee802154/6lowpan.c +++ b/net/ieee802154/6lowpan.c @@ -113,6 +113,24 @@ struct lowpan_dev_record { struct list_head list; }; +struct lowpan_fragment { + u8 in_progress; /* assembling is in progress */ + struct sk_buff *skb; /* skb to be assembled */ + u8 *data; /* data to be stored */ + struct mutex lock; /* concurency lock */ + u16 length; /* frame length to be assemled */ + u32 bytes_rcv; /* bytes received */ + u16 tag; /* current fragment tag */ + struct timer_list timer; /* assembling timer */ + struct list_head list; /* fragments list handler */ +}; + +static unsigned short fragment_tag; + +/* TODO: bind mutex and list to device */ +static LIST_HEAD(lowpan_fragments); +struct mutex flist_lock; + static inline struct lowpan_dev_info *lowpan_dev_info(const struct net_device *dev) { @@ -244,6 +262,18 @@ static u8 lowpan_fetch_skb_u8(struct sk_buff *skb) return ret; } +static u16 lowpan_fetch_skb_u16(struct sk_buff *skb) +{ + u16 ret; + + BUG_ON(skb->len < 2); + + ret = skb->data[0] | (skb->data[1] << 8); + skb_pull(skb, 2); + return ret; +} + +static netdev_tx_t lowpan_xmit(struct sk_buff *skb, struct net_device *dev); static int lowpan_header_create(struct sk_buff *skb, struct net_device *dev, unsigned short type, const void *_daddr, @@ -467,9 +497,102 @@ static int lowpan_header_create(struct sk_buff *skb, memcpy(&(sa.hwaddr), saddr, 8); mac_cb(skb)->flags = IEEE802154_FC_TYPE_DATA; + + /* frame fragmentation */ + + /* + * if payload + mac header doesn't fit MTU-sized frame + * we need to fragment it. + */ + if (skb->len > (127 - 24)) { /* MTU - MAC_HEADER_LENGTH */ + struct sk_buff *fr_skb; + u16 b_sent = 0; + unsigned short payload_len = skb->len; + int stat = 0; + + pr_debug("%s: the frame is too big (0x%x)," + "fragmentation needed, using tag = 0x%x\n", + __func__, payload_len, fragment_tag); + + fr_skb = skb_copy(skb, GFP_KERNEL); + if (!fr_skb) + goto error; + + /* 40-bit - fragment dispatch size */ + head = kzalloc(5, GFP_KERNEL); + if (!head) + goto error; + + /* first fagment header */ + head[0] = LOWPAN_DISPATCH_FRAG1 | (payload_len & 0x7); + head[1] = (payload_len >> 3) & 0xff; + head[2] = fragment_tag & 0xff; + head[3] = fragment_tag >> 8; + + + lowpan_raw_dump_inline(__func__, "first header", + head, 4); + + memcpy(skb_push(fr_skb, 4), head, 4); + skb_trim(fr_skb, LOWPAN_FRAG_SIZE); + + dev_hard_header(fr_skb, lowpan_dev_info(dev)->real_dev, + type, (void *)&da, (void *)&sa, fr_skb->len); + + /* send fragment to dev queue */ + dev_queue_xmit(fr_skb); + + /* next fragments headers */ + head[0] |= 0x20; + + lowpan_raw_dump_inline(__func__, "next headers", + head, 5); + + while (b_sent < payload_len) { + /* not the first fragment */ + if (b_sent) + skb_pull(skb, LOWPAN_FRAG_SIZE); + + pr_debug("%s: preparing fragment %d\n", + __func__, b_sent / LOWPAN_FRAG_SIZE); + + /* + * create copy of current buffer and trim it + * down to fragment size + */ + fr_skb = skb_copy(skb, GFP_KERNEL); + if (!fr_skb) + goto error; + + skb_trim(fr_skb, LOWPAN_FRAG_SIZE); + + /* add fragment header */ + head[4] = b_sent / 8; + memcpy(skb_push(fr_skb, 5), head, 5); + + b_sent += LOWPAN_FRAG_SIZE; + + lowpan_raw_dump_table(__func__, + "fragment data", fr_skb->data, fr_skb->len); + + stat = dev_hard_header(fr_skb, + lowpan_dev_info(dev)->real_dev, type, + (void *)&da, (void *)&sa, fr_skb->len); + + dev_queue_xmit(fr_skb); + } + + /* TODO: what's the correct way to skip default skb? */ + + fragment_tag++; + return stat; + } else return dev_hard_header(skb, lowpan_dev_info(dev)->real_dev, type, (void *)&da, (void *)&sa, skb->len); } +error: + kfree_skb(skb); + return -ENOMEM; } static int lowpan_skb_deliver(struct sk_buff *skb, struct ipv6hdr *hdr) @@ -511,6 +634,23 @@ static int lowpan_skb_deliver(struct sk_buff *skb, struct ipv6hdr *hdr) return stat; } +static void lowpan_fragment_timer_expired(unsigned long tag) +{ + struct lowpan_fragment *entry, *tmp; + + pr_debug("%s: timer expired for frame with tag %lu\n", __func__, tag); + + mutex_lock(&flist_lock); + list_for_each_entry_safe(entry, tmp, &lowpan_fragments, list) + if (entry->tag == tag) { + list_del(&entry->list); + kfree(entry->data); + kfree(entry); + break; + } + mutex_unlock(&flist_lock); +} + static int lowpan_process_data(struct sk_buff *skb) { @@ -525,6 +665,139 @@ lowpan_process_data(struct sk_buff *skb) if (skb->len < 2) goto drop; iphc0 = lowpan_fetch_skb_u8(skb); + + /* fragments assmebling */ + switch (iphc0 & 0xf8) { + /* first fragment of the frame */ + case LOWPAN_DISPATCH_FRAG1: + { + struct lowpan_fragment *entry, *frame; + u16 tag; + + lowpan_raw_dump_inline(__func__, "first frame fragment header", + skb->data, 3); + + tmp = lowpan_fetch_skb_u8(skb); + tag = lowpan_fetch_skb_u16(skb); + + /* + * check if frame assembling with the same tag is + * already in progress + */ + rcu_read_lock(); + list_for_each_entry_rcu(entry, &lowpan_fragments, list) + if (entry->tag == tag) { + pr_debug("%s ERROR: frame with this tag is" + "alredy in assembling", __func__); + goto drop_rcu; + } + rcu_read_unlock(); + + /* alloc new frame structure */ + frame = kzalloc(sizeof(struct lowpan_fragment), GFP_KERNEL); + if (!frame) + goto drop; + + INIT_LIST_HEAD(&frame->list); + + frame->bytes_rcv = 0; + frame->length = (iphc0 & 7) | (tmp << 3); + frame->tag = tag; + /* allocate buffer for frame assembling */ + frame->data = kzalloc(frame->length, GFP_KERNEL); + if (!frame->data) { + kfree(frame); + goto drop; + } + + pr_debug("%s: frame to be assembled: length = 0x%x, " + "tag = 0x%x\n", __func__, frame->length, frame->tag); + + init_timer(&frame->timer); + /* (number of fragments) * (fragment processing time-out) */ + frame->timer.expires = jiffies + + (frame->length / LOWPAN_FRAG_SIZE + 1) * LOWPAN_FRAG_TIMEOUT; + frame->timer.data = tag; + frame->timer.function = lowpan_fragment_timer_expired; + + add_timer(&frame->timer); + + mutex_lock(&flist_lock); + list_add_tail(&frame->list, &lowpan_fragments); + mutex_unlock(&flist_lock); + + return kfree_skb(skb), 0; + } + /* second and next fragment of the frame */ + case LOWPAN_DISPATCH_FRAGN: + { + u16 tag; + struct lowpan_fragment *entry, *t; + + lowpan_raw_dump_inline(__func__, "next fragment header", + skb->data, 4); + + lowpan_fetch_skb_u8(skb); /* skip frame length byte */ + tag = lowpan_fetch_skb_u16(skb); + + rcu_read_lock(); + list_for_each_entry_rcu(entry, &lowpan_fragments, list) + if (entry->tag == tag) + break; + rcu_read_unlock(); + + if (entry->tag != tag) { + pr_debug("%s ERROR: no frame structure found for this" + "fragment", __func__); + goto drop; + } + + tmp = lowpan_fetch_skb_u8(skb); /* fetch offset */ + + lowpan_raw_dump_table(__func__, "next fragment payload", + skb->data, skb->len); + + /* if payload fits buffer, copy it */ + if ((tmp * 8 + skb->len) <= entry->length) /* TODO: likely? */ + memcpy(entry->data + tmp * 8, skb->data, skb->len); + else + goto drop; + + entry->bytes_rcv += skb->len; + + pr_debug("%s: frame length = 0x%x, bytes received = 0x%x\n", + __func__, entry->length, entry->bytes_rcv); + + /* frame assembling complete */ + if (entry->bytes_rcv == entry->length) { + struct sk_buff *tmp = skb; + + mutex_lock(&flist_lock); + list_for_each_entry_safe(entry, t, &lowpan_fragments, list) + if (entry->tag == tag) { + list_del(&entry->list); + /* copy and clear skb */ + skb = skb_copy_expand(skb, entry->length, skb_tailroom(skb), GFP_KERNEL); + skb_pull(skb, skb->len); + /* copy new data to skb */ + memcpy(skb_push(skb, entry->length), entry->data, entry->length); + kfree_skb(tmp); + del_timer(&entry->timer); + kfree(entry->data); + kfree(entry); + + iphc0 = lowpan_fetch_skb_u8(skb); + break; + } + mutex_unlock(&flist_lock); + break; + } + return kfree_skb(skb), 0; + } + default: + break; + } + iphc1 = lowpan_fetch_skb_u8(skb); _saddr = mac_cb(skb)->sa.hwaddr; @@ -674,6 +947,8 @@ lowpan_process_data(struct sk_buff *skb) lowpan_raw_dump_table(__func__, "raw header dump", (u8 *)&hdr, sizeof(hdr)); return lowpan_skb_deliver(skb, &hdr); +drop_rcu: + rcu_read_unlock(); drop: kfree(skb); return -EINVAL; @@ -765,8 +1040,15 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev, goto drop; /* check that it's our buffer */ - if ((skb->data[0] & 0xe0) == 0x60) + switch (skb->data[0] & 0xe0) { + case 0x60: /* ipv6 datagram */ + case 0xc0: /* first fragment header */ + case 0xe0: /* next fragments headers */ lowpan_process_data(skb); + break; + default: + break; + } return NET_RX_SUCCESS; @@ -793,6 +1075,8 @@ static int lowpan_newlink(struct net *src_net, struct net_device *dev, lowpan_dev_info(dev)->real_dev = real_dev; mutex_init(&lowpan_dev_info(dev)->dev_list_mtx); + mutex_init(&flist_lock); + entry = kzalloc(sizeof(struct lowpan_dev_record), GFP_KERNEL); if (!entry) return -ENOMEM; diff --git a/net/ieee802154/6lowpan.h b/net/ieee802154/6lowpan.h index 5d8cf80..e8e57c4 100644 --- a/net/ieee802154/6lowpan.h +++ b/net/ieee802154/6lowpan.h @@ -159,6 +159,9 @@ #define LOWPAN_DISPATCH_FRAG1 0xc0 /* 11000xxx */ #define LOWPAN_DISPATCH_FRAGN 0xe0 /* 11100xxx */ +#define LOWPAN_FRAG_SIZE 40 /* fragment payload size */ +#define LOWPAN_FRAG_TIMEOUT (HZ * 2) /* processing time: 2 sec */ + /* * Values of fields within the IPHC encoding first byte * (C stands for compressed and I for inline) -- 1.7.2.5