[ovs-dev] [PATCH v7] datapath: Add Stateless TCP Tunneling protocol.

[Pravin Shelar]

On Mon, Apr 20, 2015 at 3:36 PM, Jesse Gross <jesse at nicira.com> wrote:
> On Mon, Apr 20, 2015 at 1:29 PM, Pravin B Shelar <pshelar at nicira.com> wrote:
>> diff --git a/datapath/linux/compat/stt.c b/datapath/linux/compat/stt.c
>> new file mode 100644
>> index 0000000..209bf1a
>> --- /dev/null
>> +++ b/datapath/linux/compat/stt.c
>> +static void update_headers(struct sk_buff *skb, bool head,
>> +                              unsigned int l4_offset, unsigned int hdr_len,
>> +                              bool ipv4, u32 tcp_seq)
> [...]
>> +       skb->truesize = SKB_TRUESIZE(skb_end_offset(skb)) + skb->data_len;
>> +}
>
> I wonder if there are any possible edge cases with resetting truesize
> where the packet is still in someone's transmit queue (such as if we
> are looping back packet). Do we need to orphan it first?
>
ok, I will orphan it in update_headers.

>> +static void stt_rcv(struct stt_sock *stt_sock, struct sk_buff *skb)
>> +{
> [...]
>> +       if (skb->next) {
>> +               err = coalesce_skb(&skb);
>> +               if (err)
>> +                       goto drop;
>> +       }
>> +
>> +       err = iptunnel_pull_header(skb,
>> +                                  sizeof(struct stthdr) + STT_ETH_PAD,
>> +                                  htons(ETH_P_TEB));
>
> This version of coalesce_skb() doesn't create fully formed skbs (any
> remaining pieces are in skb->next instead of a frag_list), right? That
> means that iptunnel_pull_header() potentially won't be able to access
> the data.

right. I want to avoid setting and resetting skb->next and fraglist
pointer. So I will only do it if iptunnel_pull_header fails to do it
in first attempt. I think it should be pretty rare to get skb without
the stt header in first skb.