| Message ID | 161047352593.4003084.6778762780747210369.stgit@firesoul (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf: New approach for BPF MTU handling | expand |
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@mail.gmail.com/ > > 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@redhat.com> > --- > 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? Thanks, John
On Thu, 14 Jan 2021 01:03:33 -0800 John Fastabend <john.fastabend@gmail.com> 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@mail.gmail.com/ > > > > 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@redhat.com> > > --- > > 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
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 1ec3ac5d5bbf..438943f98a9c 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3930,11 +3930,38 @@ 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) +{ + 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) { 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 55499b017a42..51bc7f079958 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -2194,28 +2194,13 @@ static inline void net_timestamp_set(struct sk_buff *skb) bool is_skb_forwardable(const struct net_device *dev, const struct sk_buff *skb) { - unsigned int len; - - if (!(dev->flags & IFF_UP)) - return false; - - len = dev->mtu + dev->hard_header_len + VLAN_HLEN; - 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; + return __is_skb_forwardable(dev, skb, true); } EXPORT_SYMBOL_GPL(is_skb_forwardable); int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb) { - int ret = ____dev_forward_skb(dev, skb); + int ret = ____dev_forward_skb(dev, skb, true); if (likely(!ret)) { skb->protocol = eth_type_trans(skb, dev); 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; } static inline int __bpf_rx_skb_no_mac(struct net_device *dev, struct sk_buff *skb) { - int ret = ____dev_forward_skb(dev, skb); + int ret = ____dev_forward_skb(dev, skb, false); if (likely(!ret)) { skb->dev = dev; @@ -2480,7 +2488,7 @@ int skb_do_redirect(struct sk_buff *skb) goto out_drop; dev = ops->ndo_get_peer_dev(dev); if (unlikely(!dev || - !is_skb_forwardable(dev, skb) || + !(dev->flags & IFF_UP) || net_eq(net, dev_net(dev)))) goto out_drop; skb->dev = dev;
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@mail.gmail.com/ 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@redhat.com> --- include/linux/netdevice.h | 31 +++++++++++++++++++++++++++++-- net/core/dev.c | 19 ++----------------- net/core/filter.c | 14 +++++++++++--- 3 files changed, 42 insertions(+), 22 deletions(-)