On Thu, 14 Jan 2021 01:03:33 -0800 John Fastabend <john.fastabend@xxxxxxxxx> wrote: > Jesper Dangaard Brouer wrote: > > The use-case for dropping the MTU check when TC-BPF does redirect to > > ingress, is described by Eyal Birger in email[0]. The summary is the > > ability to increase packet size (e.g. with IPv6 headers for NAT64) and > > ingress redirect packet and let normal netstack fragment packet as needed. > > > > [0] https://lore.kernel.org/netdev/CAHsH6Gug-hsLGHQ6N0wtixdOa85LDZ3HNRHVd0opR=19Qo4W4Q@xxxxxxxxxxxxxx/ > > > > V9: > > - Make net_device "up" (IFF_UP) check explicit in skb_do_redirect > > > > V4: > > - Keep net_device "up" (IFF_UP) check. > > - Adjustment to handle bpf_redirect_peer() helper > > > > Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> > > --- > > include/linux/netdevice.h | 31 +++++++++++++++++++++++++++++-- > > net/core/dev.c | 19 ++----------------- > > net/core/filter.c | 14 +++++++++++--- > > 3 files changed, 42 insertions(+), 22 deletions(-) > > > > [...] > > > diff --git a/net/core/filter.c b/net/core/filter.c > > index 3f2e593244ca..1908800b671c 100644 > > --- a/net/core/filter.c > > +++ b/net/core/filter.c > > @@ -2083,13 +2083,21 @@ static const struct bpf_func_proto bpf_csum_level_proto = { > > > > static inline int __bpf_rx_skb(struct net_device *dev, struct sk_buff *skb) > > { > > - return dev_forward_skb(dev, skb); > > > + int ret = ____dev_forward_skb(dev, skb, false); > > + > > + if (likely(!ret)) { > > + skb->protocol = eth_type_trans(skb, dev); > > + skb_postpull_rcsum(skb, eth_hdr(skb), ETH_HLEN); > > + ret = netif_rx(skb); > > + } > > + > > + return ret; > > How about putting above block into a dev.c routine call it > > dev_forward_skb_nomtu(...) > > or something like that. Then we keep this code next to its pair > with mtu check, dev_forward_skb(). > > dev_forward_skb() also uses netif_rx_internal() looks like maybe we should > just do the same here? I love the idea. I'm coding it up and it looks much nicer. And yes we obviously can use netif_rx_internal() once the code in core/dev.c -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
