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.
> +
> + 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.
> 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.
> } 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.
- Alex
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