From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by passt.top (Postfix) with ESMTP id 22E7E5A026F for ; Sun, 7 Jan 2024 16:00:32 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1704639631; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6d/c9gGdNNGXBHOxcV6YmV8KsMWsI0ZXoOiydnf6TM0=; b=ZljzxvC5u+wVtJdRCC5ea6unGecaiCfyjBfk6A3Dl5XynnRcEkwOGHi11BKn6UCGCarT8/ EDN/+jlc6F/S7ApeF79OVClIBf9xITUmFZtROfVM4mCB3EWewrubHreRWk4qsKXsijWG0A Ddo9rylXbDX2fn56mJWCoMOGidtgcFU= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-569-PzE9B5p_NM2HWUsvFeyJrw-1; Sun, 07 Jan 2024 10:00:27 -0500 X-MC-Unique: PzE9B5p_NM2HWUsvFeyJrw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 24BD4101A555; Sun, 7 Jan 2024 15:00:27 +0000 (UTC) Received: from elisabeth (unknown [10.39.208.9]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 45873492BC7; Sun, 7 Jan 2024 15:00:25 +0000 (UTC) Date: Sun, 7 Jan 2024 15:59:53 +0100 From: Stefano Brivio To: David Gibson Subject: Re: [PATCH v2 04/12] icmp: Don't attempt to handle "wrong direction" ping socket traffic Message-ID: <20240107155953.4c7d0e18@elisabeth> In-Reply-To: References: <20231221065327.1307827-1-david@gibson.dropbear.id.au> <20231221065327.1307827-5-david@gibson.dropbear.id.au> <20240106165911.03b8119a@elisabeth> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.9 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: 6WM4YIDAESNR6WQIBSFNLQ7TDXLI7ZGN X-Message-ID-Hash: 6WM4YIDAESNR6WQIBSFNLQ7TDXLI7ZGN X-MailFrom: sbrivio@redhat.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: passt-dev@passt.top X-Mailman-Version: 3.3.8 Precedence: list List-Id: Development discussion and patches for passt Archived-At: Archived-At: List-Archive: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Sun, 7 Jan 2024 11:37:46 +1100 David Gibson wrote: > On Sat, Jan 06, 2024 at 04:59:11PM +0100, Stefano Brivio wrote: > > On Thu, 21 Dec 2023 17:53:19 +1100 > > David Gibson wrote: > > > > > Linux ICMP "ping" sockets are very specific in what they do. They let > > > userspace send ping requests (ICMP_ECHO or ICMP6_ECHO_REQUEST), and receive > > > matching replies (ICMP_ECHOREPLY or ICMP6_ECHO_REPLY). They don't let you > > > intercept or handle incoming ping requests. > > > > Right... I don't know exactly what I was trying to do with this, back > > then. By the way this is the main reason why it took me a while to > > review this series... did I really write all those checks without a > > purpose? :) Well, it looks like it. > > > > Anyway, if you look at ping_err() in net/ipv4/ping.c, you'll see that > > among the messages which can be sent back as error (they're received on > > the socket causing the error -- same as ICMP messages you get on a UDP > > socket for port unreachable), ICMP_ECHO is allowed (see > > ping_supported()). > > > > I think I just used that ping_supported() function to find out which > > messages we could get on the socket. But we're not going to get those > > anyway. > > Right. > > > By the way, ICMP{,V6}_EXT_ECHO{,_REQUEST} support (RFC 8335, PROBE > > messages) was added a while ago (kernel commit 08baf54f01f5 "net: add > > support for sending RFC 8335 PROBE messages")... we should add that at > > some point, it's kind of trivial. > > Indeed. Want to make a BZ for it so we don't forget? Done, it's https://bugs.passt.top/show_bug.cgi?id=78. > > > In the case of passt/pasta that means we can process echo requests from tap > > > and forward them to a ping socket, then take the replies from the ping > > > socket and forward them to tap. We can't do the reverse: take echo > > > requests from the host and somehow forward them to the guest. There's > > > really no way for something outside to initiate a ping to a passt/pasta > > > connected guest and if there was we'd need an entirely different mechanism > > > to handle it. > > > > > > However, we have some logic to deal with packets going in that reverse > > > direction. Remove it, since it can't ever be used that way. While we're > > > there use defines for the ICMPv6 types, instead of open coded type values. > > > > I guess this last sentence only applied to a previous version of your > > patch. It doesn't matter so much, but it would be nice to drop if you > > re-spin. > > Uh... no.. that change is right: > > [snip] > > > @@ -222,7 +219,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af, > > > if (!ih) > > > return 1; > > > > > > - if (ih->icmp6_type != 128 && ih->icmp6_type != 129) > > > + if (ih->icmp6_type != ICMPV6_ECHO_REQUEST) > > here. Ah, sorry, I missed this one. -- Stefano