Re: [MPTCP] [PRE-RFC 4/6] mptcp: queue data for mptcp level retransmission

[Florian Westphal <fw at strlen.de>]

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Paolo Abeni <pabeni(a)redhat.com> wrote:
> keep the send page fragment on an MPTCP level retransmission queue.
> the queue entries are allocated inside the page frag allocator,
> acquiring an additional reference to the page for each list entry.
> 
> Also switch to a custom page frag refill function, to ensure that
> the current page fragment can always host an MPTCP rtx queue entry.
> 
> The MPTCP rtx queue is flushed at socket destroy() time.

> +/* ensure we get enough memory for the frag hdr, beyond some minimal amount of
> + * data
> + */
> +bool mptcp_page_frag_refill(struct sock *sk, struct page_frag *pfrag)
> +{
> +	if (likely(skb_page_frag_refill(32U + sizeof(struct mptcp_data_frag),
> +					pfrag, sk->sk_allocation)))

Where is that 32U coming from?

> +static inline struct mptcp_data_frag *
> +mptcp_carve_data_frag(const struct mptcp_sock *msk, struct page_frag *pfrag,
> +		      int offset)
> +{
> +	struct mptcp_data_frag *dfrag;
> +
> +	offset = ALIGN(offset, BITS_PER_LONG / 8);

sizeof(long)?

The concept of keeping page frags for rexmit looks good to me, thanks Paolo
for working on this.