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/ > > 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/include/linux/netdevice.h b/include/linux/netdevice.h > index 964b494b0e8d..bd02ddab8dfe 100644 > --- a/include/linux/netdevice.h > +++ b/include/linux/netdevice.h > @@ -3891,11 +3891,38 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb); > bool is_skb_forwardable(const struct net_device *dev, > const struct sk_buff *skb); > > +static __always_inline bool __is_skb_forwardable(const struct net_device *dev, > + const struct sk_buff *skb, > + const bool check_mtu) It looks like if check_mtu=false then this is just an interface up check. Can we leave is_skb_forwardable logic alone and just change the spots where this is called with false to something with a name that describes the check, such as is_dev_up(dev). I think it will make this change smaller and the code easier to read. Did I miss something? > +{ > + const u32 vlan_hdr_len = 4; /* VLAN_HLEN */ > + unsigned int len; > + > + if (!(dev->flags & IFF_UP)) > + return false; > + > + if (!check_mtu) > + return true; > + > + len = dev->mtu + dev->hard_header_len + vlan_hdr_len; > + if (skb->len <= len) > + return true; > + > + /* if TSO is enabled, we don't care about the length as the packet > + * could be forwarded without being segmented before > + */ > + if (skb_is_gso(skb)) > + return true; > + > + return false; > +} > + > static __always_inline int ____dev_forward_skb(struct net_device *dev, > - struct sk_buff *skb) > + struct sk_buff *skb, > + const bool check_mtu) > { I guess you will get some duplication here if you have a dev_forward_skb() and a dev_forward_skb_nocheck() or something. Take it or leave it. I know I've added my share of bool swivel bits like this, but better to avoid it if possible IMO. Other than style aspects it looks correct to me. > if (skb_orphan_frags(skb, GFP_ATOMIC) || > - unlikely(!is_skb_forwardable(dev, skb))) { > + unlikely(!__is_skb_forwardable(dev, skb, check_mtu))) { > atomic_long_inc(&dev->rx_dropped); > kfree_skb(skb); > return NET_RX_DROP; > diff --git a/net/core/dev.c b/net/core/dev.c > index 9499a414d67e..445ccf92c149 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -2188,28 +2188,13 @@ static inline void net_timestamp_set(struct sk_buff *skb) >
