Re: [PATCH net-next v8 14/15] quic: add packet builder base

On Thu, Jan 29, 2026 at 11:40 AM Paolo Abeni <[email protected]> wrote:
>
> On 1/26/26 3:51 PM, Xin Long wrote:
> > +/* Configure the QUIC packet header and routing based on encryption level and path. */
> > +int quic_packet_config(struct sock *sk, u8 level, u8 path)
> > +{
> > +     struct quic_conn_id_set *dest = quic_dest(sk), *source = quic_source(sk);
> > +     struct quic_packet *packet = quic_packet(sk);
> > +     struct quic_config *c = quic_config(sk);
> > +     u32 hlen = QUIC_HLEN;
> > +
> > +     /* If packet already has data, no need to reconfigure. */
> > +     if (!quic_packet_empty(packet))
> > +             return 0;
> > +
> > +     packet->ack_eliciting = 0;
> > +     packet->frame_len = 0;
> > +     packet->ipfragok = 0;
> > +     packet->padding = 0;
> > +     packet->frames = 0;
> > +     hlen += QUIC_PACKET_NUMBER_LEN; /* Packet number length. */
> > +     hlen += quic_conn_id_choose(dest, path)->len; /* DCID length. */
> > +     if (level) {
> > +             hlen += 1; /* Length byte for DCID. */
> > +             hlen += 1 + quic_conn_id_active(source)->len; /* Length byte + SCID length. */
> > +             if (level == QUIC_CRYPTO_INITIAL) /* Include token for Initial packets. */
> > +                     hlen += quic_var_len(quic_token(sk)->len) + quic_token(sk)->len;
> > +             hlen += QUIC_VERSION_LEN; /* Version length. */
> > +             hlen += QUIC_PACKET_LENGTH_LEN; /* Packet length field length. */
> > +             /* Allow fragmentation if PLPMTUD is enabled, as it no longer relies on ICMP
> > +              * Toobig messages to discover the path MTU.
> > +              */
> > +             packet->ipfragok = !!c->plpmtud_probe_interval;
> > +     }
> > +     packet->level = level;
> > +     packet->len = (u16)hlen;
> > +     packet->overhead = (u8)hlen;
>
> Given the above math, it looks like hlen can never be > 255, but
> possibly a DEBUG_NET_WARN_ON_ONCE() could save from future bug and make
> the code more clear?
>
sounds good.

> > +
> > +     if (packet->path != path) { /* If the path changed, update and reset routing cache. */
> > +             packet->path = path;
> > +             __sk_dst_reset(sk);
> > +     }
> > +
> > +     /* Perform routing and MSS update for the configured packet. */
> > +     if (quic_packet_route(sk) < 0)
> > +             return -1;
> > +     return 0;
> > +}
> > +
> > +static void quic_packet_encrypt_done(struct sk_buff *skb, int err)
> > +{
> > +     /* Free it for now, future patches will implement the actual deferred transmission logic. */
> > +     kfree_skb(skb);
> > +}
> > +
> > +/* Coalescing Packets. */
> > +static int quic_packet_bundle(struct sock *sk, struct sk_buff *skb)
> > +{
> > +     struct quic_skb_cb *head_cb, *cb = QUIC_SKB_CB(skb);
> > +     struct quic_packet *packet = quic_packet(sk);
> > +     struct sk_buff *p;
> > +
> > +     if (!packet->head) { /* First packet to bundle: initialize the head. */
> > +             packet->head = skb;
> > +             cb->last = skb;
> > +             goto out;
> > +     }
> > +
> > +     /* If bundling would exceed MSS, flush the current bundle. */
> > +     if (packet->head->len + skb->len >= packet->mss[0]) {
> > +             quic_packet_flush(sk);
> > +             packet->head = skb;
> > +             cb->last = skb;
> > +             goto out;
>
> The same code is duplicate a few lines above; you could reduce
> duplication jumping to a common label.
>
will add a goto label at the end for this:

init:
        packet->head = skb;
        cb->last = skb;
        goto out;

Thanks.