On Mon, Jul 24, 2023 at 09:13 PM -07, Yan Zhai wrote:
skb_do_redirect returns various of values: error code (negative), 0 (success), and some positive status code, e.g. NET_XMIT_CN, NET_RX_DROP. Such code are not handled at lwt xmit hook in function ip_finish_output2 and ip6_finish_output, which can cause unexpected problems. This change converts the positive status code to proper error code.
Suggested-by: Stanislav Fomichev sdf@google.com Reported-by: Jordan Griege jgriege@cloudflare.com Signed-off-by: Yan Zhai yan@cloudflare.com
v3: converts also RX side return value in addition to TX values v2: code style change suggested by Stanislav Fomichev
net/core/filter.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/net/core/filter.c b/net/core/filter.c index 06ba0e56e369..3e232ce11ca0 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -2095,7 +2095,12 @@ 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_nomtu(dev, skb);
- int ret = dev_forward_skb_nomtu(dev, skb);
- if (unlikely(ret > 0))
return -ENETDOWN;- return 0;
} static inline int __bpf_rx_skb_no_mac(struct net_device *dev, @@ -2106,6 +2111,8 @@ static inline int __bpf_rx_skb_no_mac(struct net_device *dev, if (likely(!ret)) { skb->dev = dev; ret = netif_rx(skb);
- } else if (ret > 0) {
return -ENETDOWN;return ret; @@ -2129,6 +2136,9 @@ static inline int __bpf_tx_skb(struct net_device *dev, struct sk_buff *skb) ret = dev_queue_xmit(skb); dev_xmit_recursion_dec();
- if (unlikely(ret > 0))
ret = net_xmit_errno(ret);- return ret;
}
net_xmit_errno maps NET_XMIT_DROP to -ENOBUFS. It would make sense to me to map NET_RX_DROP to -ENOBUFS as well, instead of -ENETDOWN, to be consistent.
It looks like the Fixes tag for this should point to the change that introduced BPF for LWT:
Fixes: 3a0af8fd61f9 ("bpf: BPF for lightweight tunnel infrastructure")