RE: [PATCH bpf-next V11 5/7] bpf: drop MTU check when doing TC-BPF redirect to ingress
From: John Fastabend <john.fastabend@gmail.com>
Date: 2021-01-14 09:05:01
Also in:
netdev
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/ (local) 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 <redacted> --- include/linux/netdevice.h | 31 +++++++++++++++++++++++++++++-- net/core/dev.c | 19 ++----------------- net/core/filter.c | 14 +++++++++++--- 3 files changed, 42 insertions(+), 22 deletions(-)
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quoted hunk ↗ jump to hunk
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