netdev - [RFC PATCH net-next] bpf, net: support redirecting to ifb with bpf

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Message-Id: <20230328115105.13553-1-laoar.shao@gmail.com>
Date:   Tue, 28 Mar 2023 11:51:05 +0000
From:   Yafang Shao <laoar.shao@...il.com>
To:     davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, ast@...nel.org, daniel@...earbox.net,
        hawk@...nel.org, john.fastabend@...il.com
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org,
        Yafang Shao <laoar.shao@...il.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Tonghao Zhang <xiangxia.m.yue@...il.com>
Subject: [RFC PATCH net-next] bpf, net: support redirecting to ifb with bpf

In our container environment, we are using EDT-bpf to limit the egress
bandwidth. EDT-bpf can be used to limit egress only, but can't be used
to limit ingress. Some of our users also want to limit the ingress
bandwidth. But after applying EDT-bpf, which is based on clsact qdisc,
it is impossible to limit the ingress bandwidth currently, due to some
reasons,
1). We can't add ingress qdisc
The ingress qdisc can't coexist with clsact qdisc as clsact has both
ingress and egress handler. So our traditional method to limit ingress
bandwidth can't work any more.
2). We can't redirect ingress packet to ifb with bpf
By trying to analyze if it is possible to redirect the ingress packet to
ifb with a bpf program, we find that the ifb device is not supported by
bpf redirect yet.

This patch tries to resolve it by supporting redirecting to ifb with bpf
program.

There're some other users who want to resolve this issue as well. By
searching it in the lore, it shows that Jesper[1] and Tonghao[2] used to
propose similar solution. This proposal is almost the same with Jesper's
proposal, so I add Jesper's Co-developed-by here.

[1]. https://lore.kernel.org/bpf/160650040800.2890576.9811290366501747109.stgit@firesoul/
[2]. https://lore.kernel.org/netdev/20220324135653.2189-1-xiangxia.m.yue@gmail.com/

Co-developed-by: Jesper Dangaard Brouer <brouer@...hat.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>
Signed-off-by: Yafang Shao <laoar.shao@...il.com>
Cc: Jesper Dangaard Brouer <brouer@...hat.com>
Cc: Tonghao Zhang <xiangxia.m.yue@...il.com>
---
 net/core/dev.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 18dc8d7..3e63f6b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3956,6 +3956,7 @@ int dev_loopback_xmit(struct net *net, struct sock *sk, struct sk_buff *skb)
 		return NULL;
 	case TC_ACT_REDIRECT:
 		/* No need to push/pop skb's mac_header here on egress! */
+		skb_set_redirected(skb, skb->tc_at_ingress);
 		skb_do_redirect(skb);
 		*ret = NET_XMIT_SUCCESS;
 		return NULL;
@@ -5138,6 +5139,7 @@ static __latent_entropy void net_tx_action(struct softirq_action *h)
 		 * redirecting to another netdev
 		 */
 		__skb_push(skb, skb->mac_len);
+		skb_set_redirected(skb, skb->tc_at_ingress);
 		if (skb_do_redirect(skb) == -EAGAIN) {
 			__skb_pull(skb, skb->mac_len);
 			*another = true;
-- 
1.8.3.1