On 03/03/2018 05:02 PM, Daniel Axtens wrote:
>> From: Daniel Axtens <d...@axtens.net>
>>
>> SCTP GSO skbs have a gso_size of GSO_BY_FRAGS, so any sort of
>> unconditionally mangling of that will result in nonsense value
>> and would corrupt the skb later on.
>>
>> Therefore, i) add two helpers skb_increase_gso_size() and
>> skb_decrease_gso_size() that would throw a one time warning and
>> bail out for such skbs and ii) refuse and return early with an
>> error in those BPF helpers that are affected. We do need to bail
>> out as early as possible from there before any changes on the
>> skb have been performed.
>>
>> Fixes: 6578171a7ff0 ("bpf: add bpf_skb_change_proto helper")
>> Co-authored-by: Daniel Borkmann <dan...@iogearbox.net>
>> Signed-off-by: Daniel Axtens <d...@axtens.net>
>> Cc: Marcelo Ricardo Leitner <marcelo.leit...@gmail.com>
>> Acked-by: Alexei Starovoitov <a...@kernel.org>
>
> I've looked over your changes and they all look good to me.
>
>> +/* Note: Should be called only if skb_is_gso(skb) is true */
>> +static inline bool skb_is_gso_sctp(const struct sk_buff *skb)
>> +{
>> + return skb_shinfo(skb)->gso_type & SKB_GSO_SCTP;
>> +}
>> +
>
> This helper is a fantastic idea and I will send a docs update to
> highlight it.
Sounds good. There are infact several places in the code that
could make use of this right away. If you have a chance, this
could be done in net-next along with the doc update or so.
Thanks,
Daniel
