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[195.134.167.217]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4909d6f35f8sm21915255e9.13.2026.05.29.02.02.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 29 May 2026 02:02:54 -0700 (PDT) Date: Fri, 29 May 2026 11:02:52 +0200 From: Mahe Tardy To: Jordan Rife Cc: bpf@vger.kernel.org, martin.lau@linux.dev, daniel@iogearbox.net, john.fastabend@gmail.com, ast@kernel.org, andrii@kernel.org, yonghong.song@linux.dev, netdev@vger.kernel.org, netfilter-devel@vger.kernel.org, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Subject: Re: [PATCH bpf-next v7 3/7] bpf: add bpf_icmp_send kfunc Message-ID: References: <20260526153708.279717-1-mahe.tardy@gmail.com> <20260526153708.279717-4-mahe.tardy@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Thu, May 28, 2026 at 03:55:21PM -0700, Jordan Rife wrote: > On Tue, May 26, 2026 at 03:37:04PM +0000, Mahe Tardy wrote: > > [...] > > +__bpf_kfunc int bpf_icmp_send(struct __sk_buff *skb_ctx, int type, int code) > > +{ > > + struct sk_buff *skb = (struct sk_buff *)skb_ctx; > > + struct sk_buff *nskb; > > + struct sock *sk; > > + > > + sk = skb_to_full_sk(skb); > > + if (sk && sk->sk_kern_sock && > > Won't this prevent the kfunc from working for traffic emitted from > kernel sockets like those used by NFS/SMB mounts? I can imagine there > being a legitimate use case where you'd want those kind of connections > to fail fast as well by emitting ICMP*_DEST_UNREACH. I don't know much about NFS/SMB but I'd expect them to use UDP or TCP for their transport protocol, so the second half of the condition check: > > + (sk->sk_protocol == IPPROTO_ICMP || sk->sk_protocol == IPPROTO_ICMPV6)) > > + return -EBUSY; should fail. Meaning that this should be suitable for it. The goal here was to identify the ICMP kernel sockets, I think this way should be precise enough and does not require new code. The other more precise ways we thought about initially were more invasive: - exposing ipv4_icmp_sk out of net/ipv4/icmp.c to compare the pointer: not clean as other part of the code could reuse those sockets. - expose a helper like is_kernel_icmp_socket from net/ipv4/icmp.c to be used in net/core/filter.c: new exported functions. > > + > > [...]