Hi Alex,
On 16/09/14 07:57, Alexander Aring wrote:
> Hi Martin,
>
> On Mon, Sep 15, 2014 at 03:09:54PM +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.
>> It also makes the lowpan_rcv function more extendable as we
>> can support more compression schemes.
>>
>> With the above 2 lowpan_rcv is refacored so eliminate incorrect return values.
>>
>> Signed-off-by: Martin Townsend <martin.townsend@xxxxxxxxxx>
>> ---
>> include/net/6lowpan.h | 4 +--
>> net/6lowpan/iphc.c | 74 ++++++++++++++++++-------------------------
>> net/bluetooth/6lowpan.c | 26 +++++++++------
>> net/ieee802154/6lowpan_rtnl.c | 55 ++++++++++++++++++++------------
>> 4 files changed, 83 insertions(+), 76 deletions(-)
>>
>> diff --git a/include/net/6lowpan.h b/include/net/6lowpan.h
>> index d184df1..450eaaf 100644
>> --- a/include/net/6lowpan.h
>> +++ b/include/net/6lowpan.h
>> @@ -374,10 +374,10 @@ 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,
>> +int lowpan_process_data(struct sk_buff **skb_inout, 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);
>> + 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..d51e8bb 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.
>> */
>> @@ -332,14 +301,15 @@ 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,
>> +int lowpan_process_data(struct sk_buff **skb_inout, 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)
>> + u8 iphc0, u8 iphc1)
>> {
>> struct ipv6hdr hdr = {};
>> u8 tmp, num_context = 0;
>> - int err;
>> + int err = -EINVAL;
>> + struct sk_buff *skb = *skb_inout;
>>
>> raw_dump_table(__func__, "raw skb data dump uncompressed",
>> skb->data, skb->len);
>> @@ -460,7 +430,6 @@ int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
>> /* UDP data uncompression */
>> if (iphc0 & LOWPAN_IPHC_NH_C) {
>> struct udphdr uh;
>> - struct sk_buff *new;
>>
>> if (uncompress_udp_header(skb, &uh))
>> goto drop;
>> @@ -468,14 +437,15 @@ int lowpan_process_data(struct sk_buff *skb, struct net_device *dev,
>> /* replace the compressed UDP head by the uncompressed UDP
>> * header
>> */
>> - new = skb_copy_expand(skb, sizeof(struct udphdr),
>> + skb = skb_copy_expand(skb, sizeof(struct udphdr),
>> skb_tailroom(skb), GFP_ATOMIC);
>> - kfree_skb(skb);
>> -
>> - if (!new)
>> - return -ENOMEM;
>> + if (!skb) {
>> + err = -ENOMEM;
>> + goto drop;
>> + }
>>
>> - skb = new;
>> + kfree_skb(*skb_inout);
>> + *skb_inout = skb;
>>
>> skb_push(skb, sizeof(struct udphdr));
>> skb_reset_transport_header(skb);
>> @@ -499,11 +469,27 @@ 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);
>> + /* Setup skb with new uncompressed IPv6 header. */
> --- snip
>
>> + skb = skb_copy_expand(skb, sizeof(hdr), skb_tailroom(skb),
>> + GFP_ATOMIC);
>> + if (!skb)
>> + return -ENOMEM;
>> +
>> + kfree_skb(*skb_inout);
>> + *skb_inout = skb;
> --- snap
>
> Ignore the below one, I will only note about this... that we don't
> forget that.
>
> This code should be a generic function for increasing headroom for
> decompressing headers (IPv6, next hdr's). Still issues with
> consume_skb/kfree_skb here.
Shall I separate out the call at the end to lowpan_process_data of process_data to make it truely generic? Then once we rename them we get something more readable in lowpan_rcv like
lowpan_prepare_skb_for_decompression
lowpan_decompress_hdr_xxx
Then it can be used by multiple decompression schemes?
By issues with consume_skb/kfree_skb are you saying that because we have copy_expanded it the old skb should be consumed as it's not an error?
>
>> +
>> + skb_push(skb, sizeof(hdr));
>> + skb_reset_network_header(skb);
>> + skb_copy_to_linear_data(skb, &hdr, sizeof(hdr));
>> + skb->dev = dev;
>> +
>> + raw_dump_table(__func__, "raw skb data dump before receiving",
>> + skb->data, skb->len);
>> +
>> + return 0;
>>
>> drop:
>> - kfree_skb(skb);
>> - return -EINVAL;
>> + return err;
>> }
>> EXPORT_SYMBOL_GPL(lowpan_process_data);
>>
>> diff --git a/net/bluetooth/6lowpan.c b/net/bluetooth/6lowpan.c
>> index 206b65c..a4e340e 100644
>> --- a/net/bluetooth/6lowpan.c
>> +++ b/net/bluetooth/6lowpan.c
>> @@ -215,7 +215,7 @@ static int give_skb_to_upper(struct sk_buff *skb, struct net_device *dev)
>> return ret;
>> }
>>
>> -static int process_data(struct sk_buff *skb, struct net_device *netdev,
>> +static int process_data(struct sk_buff **skb_inout, struct net_device *netdev,
>> struct l2cap_chan *chan)
>> {
>> const u8 *saddr, *daddr;
>> @@ -223,6 +223,7 @@ static int process_data(struct sk_buff *skb, struct net_device *netdev,
>> struct lowpan_dev *dev;
>> struct lowpan_peer *peer;
>> unsigned long flags;
>> + struct sk_buff *skb = *skb_inout;
>>
>> dev = lowpan_dev(netdev);
>>
>> @@ -245,13 +246,12 @@ static int process_data(struct sk_buff *skb, struct net_device *netdev,
>> if (lowpan_fetch_skb_u8(skb, &iphc1))
>> goto drop;
>>
>> - return lowpan_process_data(skb, netdev,
>> + return lowpan_process_data(skb_inout, netdev,
>> saddr, IEEE802154_ADDR_LONG, EUI64_ADDR_LEN,
>> daddr, IEEE802154_ADDR_LONG, EUI64_ADDR_LEN,
>> - iphc0, iphc1, give_skb_to_upper);
>> + iphc0, iphc1);
>>
>> drop:
>> - kfree_skb(skb);
>> return -EINVAL;
>> }
>>
>> @@ -280,9 +280,6 @@ 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;
>> @@ -300,9 +297,20 @@ static int recv_pkt(struct sk_buff *skb, struct net_device *dev,
>> if (!local_skb)
>> goto drop;
>>
>> - ret = process_data(local_skb, dev, chan);
>> - if (ret != NET_RX_SUCCESS)
>> + ret = process_data(&local_skb, dev, chan);
>> + if (ret < 0) {
>> + kfree_skb(local_skb);
>> goto drop;
>> + }
>> +
>> + local_skb->protocol = htons(ETH_P_IPV6);
>> + local_skb->pkt_type = PACKET_HOST;
>> +
>> + if (give_skb_to_upper(local_skb, dev)
>> + != NET_RX_SUCCESS) {
>> + kfree_skb(local_skb);
>> + goto drop;
>> + }
>>
>> dev->stats.rx_bytes += skb->len;
>> dev->stats.rx_packets++;
>> diff --git a/net/ieee802154/6lowpan_rtnl.c b/net/ieee802154/6lowpan_rtnl.c
>> index 6591d27..d39dad8 100644
>> --- a/net/ieee802154/6lowpan_rtnl.c
>> +++ b/net/ieee802154/6lowpan_rtnl.c
>> @@ -164,14 +164,22 @@ static int lowpan_give_skb_to_devices(struct sk_buff *skb,
>> }
>> rcu_read_unlock();
>>
>> + if (stat < 0) {
>> + kfree_skb(skb);
>> + stat = NET_RX_DROP;
>> + } else {
>> + consume_skb(skb);
>> + }
> This basically works now, but it confuse developers.
>
> Look how stat is initzialed.
> There is mixed errno and NET_RX_FOO handling here. Which is part of the
> complete error handling mess. And correct freeing of skb's required a
> correct error handling.
>
> The function looks now like this:
>
> struct lowpan_dev_record *entry;
> struct sk_buff *skb_cp;
> int stat = NET_RX_SUCCESS;
>
> rcu_read_lock();
> list_for_each_entry_rcu(entry, &lowpan_devices, list)
> if (lowpan_dev_info(entry->ldev)->real_dev == skb->dev) {
> skb_cp = skb_copy(skb, GFP_ATOMIC);
> if (!skb_cp) {
> stat = -ENOMEM;
> Simple assign stat = NET_RX_DROP.
> break;
> }
>
> skb_cp->dev = entry->ldev;
> stat = netif_rx(skb_cp);
> }
> rcu_read_unlock();
>
> if (stat < 0) {
> remove brackets and check on NET_RX_DROP. or vice versa.
> kfree_skb(skb);
> stat = NET_RX_DROP;
> } else {
> consume_skb(skb);
> }
> return stat;
>
> Now if the list is empty we check if (stat < 0) with a NET_RX_FOO stuff,
> we should avoid that. I mean the current situation is because somebody
> mixed this stuff and that's why we have this now.
>
> Another developers look of some code (that's what I did) and see, aaah
> returning NET_RX_FOO so we can check on it, but at this situation he
> need to think a little bit more what it is the correct handline because
> there is still some errno conversion.
Ok, will change.
>
>> return stat;
>> }
>>
>> -static int process_data(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
>> +static int process_data(struct sk_buff **skb_inout,
>> + const struct ieee802154_hdr *hdr)
>> {
>> u8 iphc0, iphc1;
>> struct ieee802154_addr_sa sa, da;
>> void *sap, *dap;
>> + struct sk_buff *skb = *skb_inout;
>>
>> raw_dump_table(__func__, "raw skb data dump", skb->data, skb->len);
>> /* at least two bytes will be used for the encoding */
>> @@ -197,13 +205,11 @@ static int process_data(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
>> else
>> dap = &da.hwaddr;
>>
>> - return lowpan_process_data(skb, skb->dev, sap, sa.addr_type,
>> + return lowpan_process_data(skb_inout, skb->dev, sap, sa.addr_type,
>> IEEE802154_ADDR_LEN, dap, da.addr_type,
>> - IEEE802154_ADDR_LEN, iphc0, iphc1,
>> - lowpan_give_skb_to_devices);
>> + IEEE802154_ADDR_LEN, iphc0, iphc1);
>>
>> drop:
>> - kfree_skb(skb);
>> return -EINVAL;
>> }
>>
>> @@ -478,36 +484,39 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
>>
>> /* check that it's our buffer */
>> if (skb->data[0] == LOWPAN_DISPATCH_IPV6) {
>> - skb->protocol = htons(ETH_P_IPV6);
>> - skb->pkt_type = PACKET_HOST;
>> -
>> /* Pull off the 1-byte of 6lowpan header. */
>> skb_pull(skb, 1);
>>
>> - ret = lowpan_give_skb_to_devices(skb, NULL);
>> - if (ret == NET_RX_DROP)
>> - goto drop;
>> + ret = NET_RX_SUCCESS;
> We don't need to set ret here.
This will all change in my future patch to refactor this function to be more RFC compliant. Will send to linux-wpan once this is in.
>
>> } else {
>> switch (skb->data[0] & 0xe0) {
>> case LOWPAN_DISPATCH_IPHC: /* ipv6 datagram */
>> - ret = process_data(skb, &hdr);
>> - if (ret == NET_RX_DROP)
>> - goto drop;
>> + ret = process_data(&skb, &hdr);
>> + if (ret < 0)
>> + goto drop_skb;
>> break;
>> case LOWPAN_DISPATCH_FRAG1: /* first fragment header */
>> ret = lowpan_frag_rcv(skb, LOWPAN_DISPATCH_FRAG1);
>> if (ret == 1) {
>> - ret = process_data(skb, &hdr);
>> - if (ret == NET_RX_DROP)
>> - goto drop;
>> + ret = process_data(&skb, &hdr);
>> + if (ret < 0)
>> + goto drop_skb;
>> + } else if (ret < 0) {
>> + goto drop;
>> + } else {
>> + return NET_RX_SUCCESS;
>> }
>> break;
>> case LOWPAN_DISPATCH_FRAGN: /* next fragments headers */
>> ret = lowpan_frag_rcv(skb, LOWPAN_DISPATCH_FRAGN);
>> if (ret == 1) {
>> - ret = process_data(skb, &hdr);
>> - if (ret == NET_RX_DROP)
>> - goto drop;
>> + ret = process_data(&skb, &hdr);
>> + if (ret < 0)
>> + goto drop_skb;
>> + } else if (ret < 0) {
>> + goto drop;
>> + } else {
>> + return NET_RX_SUCCESS;
>> }
>> break;
>> default:
>> @@ -515,7 +524,11 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
>> }
>> }
>>
>> - return NET_RX_SUCCESS;
>> + /* Pass IPv6 packet up to next layer */
>> + skb->protocol = htons(ETH_P_IPV6);
>> + skb->pkt_type = PACKET_HOST;
>> + return lowpan_give_skb_to_devices(skb, NULL);
>> +
> Please ignore the above one, also a hint:
>
> Good that we have this now, so we can do a on the fly decompression when
> receiving FRAG1. This required setting skb->len here.
Are you saying that skb->len needs setting here? or just that to do on the fly decompression it's required?
>
> - Alex
> --
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I'll try and respin later today.
- Martin.
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