On Mon, Feb 8, 2021 at 1:48 AM Lorenz Bauer <lmb@xxxxxxxxxxxxxx> wrote:
>
> On Wed, 3 Feb 2021 at 04:17, Cong Wang <xiyou.wangcong@xxxxxxxxx> wrote:
> >
> > From: Cong Wang <cong.wang@xxxxxxxxxxxxx>
> >
> > Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> > Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
> > Cc: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
> > Cc: Lorenz Bauer <lmb@xxxxxxxxxxxxxx>
> > Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
> > ---
> > include/net/udp.h | 2 ++
> > net/ipv4/af_inet.c | 1 +
> > net/ipv4/udp.c | 34 ++++++++++++++++++++++++++++++++++
> > 3 files changed, 37 insertions(+)
> >
> > diff --git a/include/net/udp.h b/include/net/udp.h
> > index 13f9354dbd3e..b6b75cabf4e4 100644
> > --- a/include/net/udp.h
> > +++ b/include/net/udp.h
> > @@ -327,6 +327,8 @@ struct sock *__udp6_lib_lookup(struct net *net,
> > struct sk_buff *skb);
> > struct sock *udp6_lib_lookup_skb(const struct sk_buff *skb,
> > __be16 sport, __be16 dport);
> > +int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
> > + sk_read_actor_t recv_actor);
> >
> > /* UDP uses skb->dev_scratch to cache as much information as possible and avoid
> > * possibly multiple cache miss on dequeue()
> > diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
> > index d184d9379a92..4a4c6d3d2786 100644
> > --- a/net/ipv4/af_inet.c
> > +++ b/net/ipv4/af_inet.c
> > @@ -1072,6 +1072,7 @@ const struct proto_ops inet_dgram_ops = {
> > .getsockopt = sock_common_getsockopt,
> > .sendmsg = inet_sendmsg,
> > .sendmsg_locked = udp_sendmsg_locked,
> > + .read_sock = udp_read_sock,
> > .recvmsg = inet_recvmsg,
> > .mmap = sock_no_mmap,
> > .sendpage = inet_sendpage,
> > diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> > index 635e1e8b2968..6dffbcec0b51 100644
> > --- a/net/ipv4/udp.c
> > +++ b/net/ipv4/udp.c
> > @@ -1792,6 +1792,40 @@ struct sk_buff *__skb_recv_udp(struct sock *sk, unsigned int flags,
> > }
> > EXPORT_SYMBOL(__skb_recv_udp);
> >
> > +int udp_read_sock(struct sock *sk, read_descriptor_t *desc,
> > + sk_read_actor_t recv_actor)
> > +{
> > + struct sk_buff *skb;
> > + int copied = 0, err;
> > +
> > + while (1) {
> > + int offset = 0;
> > +
> > + skb = __skb_recv_udp(sk, 0, 1, &offset, &err);
>
> Seems like err isn't used outside of the loop, is that on purpose? If
> yes, how about moving the declaration of err to be with offset. Maybe
> rename to ignored?
It should be moved inside the loop.
>
> > + if (!skb)
> > + break;
> > + if (offset < skb->len) {
> > + int used;
> > + size_t len;
> > +
> > + len = skb->len - offset;
> > + used = recv_actor(desc, skb, offset, len);
> > + if (used <= 0) {
> > + if (!copied)
> > + copied = used;
> > + break;
> > + } else if (used <= len) {
>
> In which case can used be > len?
I think in splice() case it could return a larger value than 'len', but
UDP does not support splice() even after this patchset. I can change
it to 'else', or just leave it as it is, in case we will add splice() support in
the future.
Thanks.
