From: Martin KaFai Lau <martin.lau@linux.dev>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: bpf@vger.kernel.org, netdev@vger.kernel.org,
Yusuke Suzuki <yusuke.suzuki@isovalent.com>,
Julian Wiedmann <jwi@isovalent.com>,
Martin KaFai Lau <martin.lau@kernel.org>,
Jakub Kicinski <kuba@kernel.org>, Jordan Rife <jrife@google.com>
Subject: Re: [PATCH bpf] bpf: Fix metadata_dst leak __bpf_redirect_neigh_v{4,6}
Date: Fri, 3 Oct 2025 11:50:23 -0700 [thread overview]
Message-ID: <44ca44bb-a641-4d70-ad7a-96a3187706a3@linux.dev> (raw)
In-Reply-To: <20251003073418.291171-1-daniel@iogearbox.net>
On 10/3/25 12:34 AM, Daniel Borkmann wrote:
> Cilium has a BPF egress gateway feature which forces outgoing K8s Pod
> traffic to pass through dedicated egress gateways which then SNAT the
> traffic in order to interact with stable IPs outside the cluster.
>
> The traffic is directed to the gateway via vxlan tunnel in collect md
> mode. A recent BPF change utilized the bpf_redirect_neigh() helper to
> forward packets after the arrival and decap on vxlan, which turned out
> over time that the kmalloc-256 slab usage in kernel was ever-increasing.
>
> The issue was that vxlan allocates the metadata_dst object and attaches
> it through a fake dst entry to the skb. The latter was never released
> though given bpf_redirect_neigh() was merely setting the new dst entry
> via skb_dst_set() without dropping an existing one first.
Reviewed-by: Martin KaFai Lau <martin.lau@kernel.org>
next prev parent reply other threads:[~2025-10-03 18:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-03 7:34 [PATCH bpf] bpf: Fix metadata_dst leak __bpf_redirect_neigh_v{4,6} Daniel Borkmann
2025-10-03 9:42 ` Simon Horman
2025-10-03 15:01 ` Jordan Rife
2025-10-03 16:02 ` Jakub Kicinski
2025-10-03 19:24 ` Daniel Borkmann
2025-10-03 18:50 ` Martin KaFai Lau [this message]
2025-10-07 4:30 ` patchwork-bot+netdevbpf
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