Hi Alex
On 05/10/14 18:50, Alexander Aring wrote:
> Hi Martin,
>
> On Wed, Oct 01, 2014 at 01:10:22PM +0100, Martin Townsend wrote:
>> Currently there are a number of error paths in the lowpan_rcv function that
>> free the skb before returning, the patch simplifies the receive path by
>> ensuring that the skb is only freed from this function.
>>
>> Passing the skb from 6lowpan up to the higher layers is not a
>> function of IPHC. By moving it out of IPHC we also remove the
>> need to support error code returns with NET_RX codes.
> I think we should split the movement of "passing skb to higher layer"
> into a separate patch.
Wasn't it separated in v1 patch series and you asked me to combine into
one patch??
>
>> It also makes the lowpan_rcv function more extendable as we
>> can support more compression schemes.
>>
>> With the above 2 lowpan_rcv is refactored so eliminate incorrect return
>> values.
>>
>> Signed-off-by: Martin Townsend <martin.towns...@xsilon.com>
>> ---
>> include/net/6lowpan.h | 9 +++--
>> net/6lowpan/iphc.c | 92
>> ++++++++++++++++---------------------------
>> net/bluetooth/6lowpan.c | 52 ++++++++++++++++--------
>> net/ieee802154/6lowpan_rtnl.c | 66 ++++++++++++++++++++-----------
>> 4 files changed, 117 insertions(+), 102 deletions(-)
>>
>> diff --git a/include/net/6lowpan.h b/include/net/6lowpan.h
>> index d184df1..05ff67e 100644
>> --- a/include/net/6lowpan.h
>> +++ b/include/net/6lowpan.h
>> @@ -374,10 +374,11 @@ lowpan_uncompress_size(const struct sk_buff *skb, u16
>> *dgram_offset)
>>
>> typedef int (*skb_delivery_cb)(struct sk_buff *skb, struct net_device
>> *dev);
>>
>> -int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
>> - const u8 *saddr, const u8 saddr_type, const u8 saddr_len,
>> - const u8 *daddr, const u8 daddr_type, const u8 daddr_len,
>> - u8 iphc0, u8 iphc1, skb_delivery_cb skb_deliver);
>> +int
>> +lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
>> + const u8 *saddr, const u8 saddr_type, const u8 saddr_len,
>> + const u8 *daddr, const u8 daddr_type, const u8 daddr_len,
>> + u8 iphc0, u8 iphc1);
>> int lowpan_header_compress(struct sk_buff *skb, struct net_device *dev,
>> unsigned short type, const void *_daddr,
>> const void *_saddr, unsigned int len);
>> diff --git a/net/6lowpan/iphc.c b/net/6lowpan/iphc.c
>> index 142eef5..3888357 100644
>> --- a/net/6lowpan/iphc.c
>> +++ b/net/6lowpan/iphc.c
>> @@ -171,37 +171,6 @@ static int uncompress_context_based_src_addr(struct
>> sk_buff *skb,
>> return 0;
>> }
>>
>> -static int skb_deliver(struct sk_buff *skb, struct ipv6hdr *hdr,
>> - struct net_device *dev, skb_delivery_cb deliver_skb)
>> -{
>> - struct sk_buff *new;
>> - int stat;
>> -
>> - new = skb_copy_expand(skb, sizeof(struct ipv6hdr), skb_tailroom(skb),
>> - GFP_ATOMIC);
>> - kfree_skb(skb);
>> -
>> - if (!new)
>> - return -ENOMEM;
>> -
>> - skb_push(new, sizeof(struct ipv6hdr));
>> - skb_reset_network_header(new);
>> - skb_copy_to_linear_data(new, hdr, sizeof(struct ipv6hdr));
>> -
>> - new->protocol = htons(ETH_P_IPV6);
>> - new->pkt_type = PACKET_HOST;
>> - new->dev = dev;
>> -
>> - raw_dump_table(__func__, "raw skb data dump before receiving",
>> - new->data, new->len);
>> -
>> - stat = deliver_skb(new, dev);
>> -
>> - kfree_skb(new);
>> -
>> - return stat;
>> -}
>> -
>> /* Uncompress function for multicast destination address,
>> * when M bit is set.
>> */
>> @@ -332,10 +301,11 @@ err:
>> /* TTL uncompression values */
>> static const u8 lowpan_ttl_values[] = { 0, 1, 64, 255 };
>>
>> -int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
>> - const u8 *saddr, const u8 saddr_type, const u8
>> saddr_len,
>> - const u8 *daddr, const u8 daddr_type, const u8
>> daddr_len,
>> - u8 iphc0, u8 iphc1, skb_delivery_cb deliver_skb)
>> +int
>> +lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
>> + const u8 *saddr, const u8 saddr_type, const u8 saddr_len,
>> + const u8 *daddr, const u8 daddr_type, const u8 daddr_len,
>> + u8 iphc0, u8 iphc1)
>> {
>> struct ipv6hdr hdr = {};
>> u8 tmp, num_context = 0;
>> @@ -348,7 +318,7 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>> if (iphc1 & LOWPAN_IPHC_CID) {
>> pr_debug("CID flag is set, increase header with one\n");
>> if (lowpan_fetch_skb(skb, &num_context, sizeof(num_context)))
>> - goto drop;
>> + return -EINVAL;
>> }
>>
>> hdr.version = 6;
>> @@ -360,7 +330,7 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>> */
>> case 0: /* 00b */
>> if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
>> - goto drop;
>> + return -EINVAL;
>>
>> memcpy(&hdr.flow_lbl, &skb->data[0], 3);
>> skb_pull(skb, 3);
>> @@ -373,7 +343,7 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>> */
>> case 2: /* 10b */
>> if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
>> - goto drop;
>> + return -EINVAL;
>>
>> hdr.priority = ((tmp >> 2) & 0x0f);
>> hdr.flow_lbl[0] = ((tmp << 6) & 0xC0) | ((tmp >> 2) & 0x30);
>> @@ -383,7 +353,7 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>> */
>> case 1: /* 01b */
>> if (lowpan_fetch_skb(skb, &tmp, sizeof(tmp)))
>> - goto drop;
>> + return -EINVAL;
>>
>> hdr.flow_lbl[0] = (skb->data[0] & 0x0F) | ((tmp >> 2) & 0x30);
>> memcpy(&hdr.flow_lbl[1], &skb->data[0], 2);
>> @@ -400,7 +370,7 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>> if ((iphc0 & LOWPAN_IPHC_NH_C) == 0) {
>> /* Next header is carried inline */
>> if (lowpan_fetch_skb(skb, &hdr.nexthdr, sizeof(hdr.nexthdr)))
>> - goto drop;
>> + return -EINVAL;
>>
>> pr_debug("NH flag is set, next header carried inline: %02x\n",
>> hdr.nexthdr);
>> @@ -412,7 +382,7 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>> } else {
>> if (lowpan_fetch_skb(skb, &hdr.hop_limit,
>> sizeof(hdr.hop_limit)))
>> - goto drop;
>> + return -EINVAL;
>> }
>>
>> /* Extract SAM to the tmp variable */
>> @@ -431,7 +401,7 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>>
>> /* Check on error of previous branch */
>> if (err)
>> - goto drop;
>> + return -EINVAL;
>>
>> /* Extract DAM to the tmp variable */
>> tmp = ((iphc1 & LOWPAN_IPHC_DAM_11) >> LOWPAN_IPHC_DAM_BIT) & 0x03;
>> @@ -446,7 +416,7 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>> tmp);
>>
>> if (err)
>> - goto drop;
>> + return -EINVAL;
>> }
>> } else {
>> err = uncompress_addr(skb, &hdr.daddr, tmp, daddr,
>> @@ -454,28 +424,26 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>> pr_debug("dest: stateless compression mode %d dest %pI6c\n",
>> tmp, &hdr.daddr);
>> if (err)
>> - goto drop;
>> + return -EINVAL;
>> }
>>
>> /* UDP data uncompression */
>> if (iphc0 & LOWPAN_IPHC_NH_C) {
>> struct udphdr uh;
>> - struct sk_buff *new;
>>
>> if (uncompress_udp_header(skb, &uh))
>> - goto drop;
>> + return -EINVAL;
>>
>> /* replace the compressed UDP head by the uncompressed UDP
>> * header
>> */
>> - new = skb_copy_expand(skb, sizeof(struct udphdr),
>> - skb_tailroom(skb), GFP_ATOMIC);
>> - kfree_skb(skb);
>> -
>> - if (!new)
>> - return -ENOMEM;
>> + if (skb_headroom(skb) < sizeof(struct udphdr) + sizeof(hdr)) {
>> + int n = sizeof(struct udphdr) + sizeof(hdr);
> For this also a separate for "check if we have enough headroom". This
> has nothing to do with the errno fix. All patches should follow "keep it
> short and simple" not doing too much in a patch, if you can separate it
> then separate it. Then we have a better overview while reviewing and a
> nice git commit history.
>
> Also this should be "if (skb_headroom(skb) < sizeof(struct udphdr))"
> only, without the sizeof(hdr). Why you check also for space for ipv6
> header here? This is part of transport header.
If you are decompressing UDP header then you also have to decompress the
IP Header below it. This would mean that 2 pskb_expand_head calls would
be needed which could result in 2 data copies which seems a waste, why
not just do it once?
>>
>> - skb = new;
>> + err = pskb_expand_head(skb, n, 0, GFP_ATOMIC);
>> + if (unlikely(err))
>> + return err;
>> + }
>>
>> skb_push(skb, sizeof(struct udphdr));
> Here we add data for udphdr only. Then check only for headroom for
> udphdr.
>
>> skb_reset_transport_header(skb);
>> @@ -485,6 +453,13 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>> (u8 *)&uh, sizeof(uh));
>>
>> hdr.nexthdr = UIP_PROTO_UDP;
>> + } else {
> Now I see why you make "sizeof(struct udphdr) + sizeof(hdr)" Better
> remove this else branch and then simple make:
>
> "if (skb_headroom(skb) < sizeof(hdr))", then we don't need to check this
> above. This is a little bit confusing.
See above, maybe a comment would help things?
>
>> + if (skb_headroom(skb) < sizeof(hdr)) {
>> + err = pskb_expand_head(skb, sizeof(hdr), 0, GFP_ATOMIC);
>> +
> remove this whitespace.
ok.
>
>> + if (unlikely(err))
>> + return err;
>> + }
>> }
>>
>> hdr.payload_len = htons(skb->len);
>> @@ -499,11 +474,14 @@ int lowpan_process_data(struct sk_buff *skb, struct
>> net_device *dev,
>>
>> raw_dump_table(__func__, "raw header dump", (u8 *)&hdr, sizeof(hdr));
>>
>> - return skb_deliver(skb, &hdr, dev, deliver_skb);
>> + skb_push(skb, sizeof(hdr));
> Here is the push for sizeof(hdr) above we should _always_ check for
> "(skb_headroom(skb) < sizeof(hdr))".
The intention of the code is to ensure that there is enough headroom
before this push. Maybe the following pseudocode helps :)
IF UDP Hdr Compression
ensure enough room for UDP Hdr and IPv6 Hdr
make room for UDP Hdr (skb_push)
decompress UDP Hdr
ELSE
ensure enough room for IPv6 Hdr
make room for IPv6 Hdr (skb_push)
decompress IPv6 Hdr
>
>
> The code is much similar for udphdr and hdr, here.... create a static
> function in this file, then we have a generic function for this (this is
> useful for other transport header when next header compression layer
> comes mainline.
>
> protoype looks like:
>
> int skb_check_and_expand(struct sk_buff *skb, size_t len)
>
> should contain something like:
>
> if (skb_headroom(skb) < len)
> do_expand_stuff(skb....);
>
> return 0;
>
>
>> + skb_reset_network_header(skb);
>> + skb_copy_to_linear_data(skb, &hdr, sizeof(hdr));
>>
>> -drop:
>> - kfree_skb(skb);
>> - return -EINVAL;
>> + raw_dump_table(__func__, "raw skb data dump before receiving",
>> + skb->data, skb->len);
>> +
>> + return 0;
>> }
>> EXPORT_SYMBOL_GPL(lowpan_process_data);
>>
>> diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
>> index 206b65c..adfd361 100644
>> --- a/net/bluetooth/6lowpan.c
>> +++ b/net/bluetooth/6lowpan.c
>> @@ -230,36 +230,31 @@ static int process_data(struct sk_buff *skb, struct
>> net_device *netdev,
>> peer = peer_lookup_chan(dev, chan);
>> read_unlock_irqrestore(&devices_lock, flags);
>> if (!peer)
>> - goto drop;
>> + return -EINVAL;
>>
>> saddr = peer->eui64_addr;
>> daddr = dev->netdev->dev_addr;
>>
>> /* at least two bytes will be used for the encoding */
>> if (skb->len < 2)
>> - goto drop;
>> + return -EINVAL;
>>
>> if (lowpan_fetch_skb_u8(skb, &iphc0))
>> - goto drop;
>> + return -EINVAL;
>>
>> if (lowpan_fetch_skb_u8(skb, &iphc1))
>> - goto drop;
>> + return -EINVAL;
>>
>> return lowpan_process_data(skb, netdev,
>> saddr, IEEE802154_ADDR_LONG, EUI64_ADDR_LEN,
>> daddr, IEEE802154_ADDR_LONG, EUI64_ADDR_LEN,
>> - iphc0, iphc1, give_skb_to_upper);
>> -
>> -drop:
>> - kfree_skb(skb);
>> - return -EINVAL;
>> + iphc0, iphc1);
>> }
>>
>> static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
>> struct l2cap_chan *chan)
>> {
>> struct sk_buff *local_skb;
>> - int ret;
>>
>> if (!netif_running(dev))
>> goto drop;
>> @@ -280,12 +275,8 @@ static int recv_pkt(struct sk_buff *skb, struct
>> net_device *dev,
>> local_skb->protocol = htons(ETH_P_IPV6);
>> local_skb->pkt_type = PACKET_HOST;
>>
>> - skb_reset_network_header(local_skb);
>> - skb_set_transport_header(local_skb, sizeof(struct ipv6hdr));
>> -
>> if (give_skb_to_upper(local_skb, dev) != NET_RX_SUCCESS) {
>> - kfree_skb(local_skb);
>> - goto drop;
>> + goto drop_local_skb;
>> }
>>
>> dev->stats.rx_bytes += skb->len;
>> @@ -294,15 +285,40 @@ static int recv_pkt(struct sk_buff *skb, struct
>> net_device *dev,
>> kfree_skb(local_skb);
>> kfree_skb(skb);
>> } else {
>> + int ret;
>> +
>> + if (skb_cloned(skb)) {
> why is this now here? Is this necessary, we don't have such thing
> current mainline, if necessary make a separate patch for this or put it
> in the right one.
It's necessary as pskb_expand_head must have no references as you are
potentially reallocating the data part of the skb. It's position is
questionable but until other compression schemes are supported it will
suffice.
>
>> + struct sk_buff *new;
>> + int new_headroom = sizeof(struct ipv6hdr) +
>> + sizeof(struct udphdr);
>> +
>> + new = skb_copy_expand(skb, new_headroom,
>> + skb_tailroom(skb), GFP_ATOMIC);
>> + if (!new)
>> + return -ENOMEM;
>> + consume_skb(skb);
>> + skb = new;
>> + }
>> +
>> switch (skb->data[0] & 0xe0) {
>> case LOWPAN_DISPATCH_IPHC: /* ipv6 datagram */
>> +
>> + ret = process_data(skb, dev, chan);
>> + if (ret < 0)
>> + goto drop;
>> +
>> local_skb = skb_clone(skb, GFP_ATOMIC);
>> if (!local_skb)
>> goto drop;
>>
> This looks a little bit confusing, I will look at this when you sperate
> the patches. Again "move handling to upper layer" and the "check if
> expand is necessary". Then I will look at this code for correct
> "kfree_skb" and "consume_skb" calling. Hope this is okay, I need to
> decrypt this code at first. :-)
sorry, I didn't intend to writing confusing code, wait until you see the
GHC patch :)
>
> Sorry too much changes in one patch, we need to split this one. Also
> base it on bluetooth-next, should be complicated to megre this stuff for
> bluetooth with -next...
>
> - Alex
If I'm going to base it on bluetooth-next then I think the best solution
is to submit separate patches in stages
1) Checking for headroom and using pskb_expand_head for decompression:
reason for patch: saves on copying the whole structure and there
potentially might not be a copy especially if the driver allocates a
larger buffer than needed knowing that it will be decompressed
2) Move delivery out of IPHC.
reason: Ensures return value isn't a mish mash of error codes and
NET_RX_ codes, allows for better scalability as we don't have a
requirement for decompression to pass the skb onto the next layer
3) Fix lowpan_rcv
reason: Fix those pesky return value problems
Then I can go on to submit those 2 outstanding patches
4) Refactor lowpan_rcv to handle fragmented uncompressed IPv6 packets.
5) Rename process_data etc..
I think this will help Jukka as my patch currently breaks their transmit
code and we could see which part causes this. Also I'm really busy at
the moment writing a QEMU virtual device to model our transceiver so we
can get a virtual test bed working as well as a couple of other things
so it would be better for me to concentrate on one patch at a time as
time is something I don't have a lot of at the moment :)
Would you be happy with this? I know it means the bug fix happens third,
but I think it will be better in the long run.
- Martin
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