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Message-ID: <ZsSLj-fI5Hiy9aV-@shredder.mtl.com>
Date: Tue, 20 Aug 2024 15:26:55 +0300
From: Ido Schimmel <idosch@...dia.com>
To: Menglong Dong <menglong8.dong@...il.com>
Cc: kuba@...nel.org, davem@...emloft.net, edumazet@...gle.com,
pabeni@...hat.com, dsahern@...nel.org, dongml2@...natelecom.cn,
amcohen@...dia.com, gnault@...hat.com, bpoirier@...dia.com,
b.galvani@...il.com, razor@...ckwall.org, petrm@...dia.com,
linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 06/10] net: vxlan: add skb drop reasons to
vxlan_rcv()
On Thu, Aug 15, 2024 at 08:42:58PM +0800, Menglong Dong wrote:
> diff --git a/drivers/net/vxlan/vxlan_core.c b/drivers/net/vxlan/vxlan_core.c
> index e971c4785962..9a61f04bb95d 100644
> --- a/drivers/net/vxlan/vxlan_core.c
> +++ b/drivers/net/vxlan/vxlan_core.c
> @@ -1668,6 +1668,7 @@ static bool vxlan_ecn_decapsulate(struct vxlan_sock *vs, void *oiph,
> /* Callback from net/ipv4/udp.c to receive packets */
> static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
> {
> + enum skb_drop_reason reason = pskb_may_pull_reason(skb, VXLAN_HLEN);
> struct vxlan_vni_node *vninode = NULL;
> struct vxlan_dev *vxlan;
> struct vxlan_sock *vs;
> @@ -1681,7 +1682,7 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
> int nh;
>
> /* Need UDP and VXLAN header to be present */
> - if (!pskb_may_pull(skb, VXLAN_HLEN))
> + if (reason != SKB_NOT_DROPPED_YET)
> goto drop;
>
> unparsed = *vxlan_hdr(skb);
> @@ -1690,6 +1691,7 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
> netdev_dbg(skb->dev, "invalid vxlan flags=%#x vni=%#x\n",
> ntohl(vxlan_hdr(skb)->vx_flags),
> ntohl(vxlan_hdr(skb)->vx_vni));
> + reason = (u32)VXLAN_DROP_FLAGS;
I don't find "FLAGS" very descriptive. AFAICT the reason is used in
these two cases:
1. "I flag" is not set
2. The reserved fields are not zero
Maybe call it VXLAN_DROP_INVALID_HDR ?
And I agree with the comment about documenting these drop reasons like
in include/net/dropreason-core.h
> /* Return non vxlan pkt */
> goto drop;
> }
> @@ -1703,8 +1705,10 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
> vni = vxlan_vni(vxlan_hdr(skb)->vx_vni);
>
> vxlan = vxlan_vs_find_vni(vs, skb->dev->ifindex, vni, &vninode);
> - if (!vxlan)
> + if (!vxlan) {
> + reason = (u32)VXLAN_DROP_VNI;
Same comment here. Maybe VXLAN_DROP_VNI_NOT_FOUND ?
> goto drop;
> + }
>
> /* For backwards compatibility, only allow reserved fields to be
> * used by VXLAN extensions if explicitly requested.
> @@ -1717,12 +1721,16 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
> }
>
> if (__iptunnel_pull_header(skb, VXLAN_HLEN, protocol, raw_proto,
> - !net_eq(vxlan->net, dev_net(vxlan->dev))))
> + !net_eq(vxlan->net, dev_net(vxlan->dev)))) {
> + reason = SKB_DROP_REASON_NOMEM;
> goto drop;
> + }
>
> - if (vs->flags & VXLAN_F_REMCSUM_RX)
> - if (unlikely(!vxlan_remcsum(&unparsed, skb, vs->flags)))
> + if (vs->flags & VXLAN_F_REMCSUM_RX) {
> + reason = vxlan_remcsum(&unparsed, skb, vs->flags);
> + if (unlikely(reason != SKB_NOT_DROPPED_YET))
> goto drop;
> + }
>
> if (vxlan_collect_metadata(vs)) {
> IP_TUNNEL_DECLARE_FLAGS(flags) = { };
> @@ -1732,8 +1740,10 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
> tun_dst = udp_tun_rx_dst(skb, vxlan_get_sk_family(vs), flags,
> key32_to_tunnel_id(vni), sizeof(*md));
>
> - if (!tun_dst)
> + if (!tun_dst) {
> + reason = SKB_DROP_REASON_NOMEM;
> goto drop;
> + }
>
> md = ip_tunnel_info_opts(&tun_dst->u.tun_info);
>
> @@ -1757,12 +1767,15 @@ static int vxlan_rcv(struct sock *sk, struct sk_buff *skb)
> * is more robust and provides a little more security in
> * adding extensions to VXLAN.
> */
> + reason = (u32)VXLAN_DROP_FLAGS;
> goto drop;
> }
>
> if (!raw_proto) {
> - if (!vxlan_set_mac(vxlan, vs, skb, vni))
> + if (!vxlan_set_mac(vxlan, vs, skb, vni)) {
> + reason = (u32)VXLAN_DROP_MAC;
The function drops the packet for various reasons:
1. Source MAC is equal to the VXLAN device's MAC
2. Source MAC is invalid (all zeroes or multicast)
3. Trying to migrate a static entry or one pointing to a nexthop
They are all quite obscure so it might be fine to fold them under the
same reason, but I can't find a descriptive name.
If you split 1-2 to one reason and 3 to another, then they can become
VXLAN_DROP_INVALID_SMAC and VXLAN_DROP_ENTRY_EXISTS
> goto drop;
> + }
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