From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by passt.top (Postfix) with ESMTP id C13095A026D for ; Sat, 6 Jan 2024 16:59:35 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1704556774; 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=2ovXCpOCPwqTK05bn1hzTzZIa1OK44XibPwWaYYQN3Q=; b=KI+nwXzpkfXiUFNpMS6kP3pGymAXlsKyfanecFk3FZku5fjTw2svREe1ywgbHpwB5bcHyP vATaV3V6Gth1kQMyb79Dg/yFv3WAhQStCze0PO/VwBK0sThcH/Fy/d/9vfAORmIdtjkPwS cyBNazRvpQm+tfi0pYLq+Vx312WE5k8= 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-296-O_lgg9vtMcaGSWaL47Xtsw-1; Sat, 06 Jan 2024 10:59:27 -0500 X-MC-Unique: O_lgg9vtMcaGSWaL47Xtsw-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (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 90D49832D1A; Sat, 6 Jan 2024 15:59:27 +0000 (UTC) Received: from elisabeth (unknown [10.39.208.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C2ECCC15968; Sat, 6 Jan 2024 15:59:26 +0000 (UTC) Date: Sat, 6 Jan 2024 16:59:11 +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: <20240106165911.03b8119a@elisabeth> In-Reply-To: <20231221065327.1307827-5-david@gibson.dropbear.id.au> References: <20231221065327.1307827-1-david@gibson.dropbear.id.au> <20231221065327.1307827-5-david@gibson.dropbear.id.au> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.8 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: 2RIN5Z3GY4NLHB73TL6CWSMZZRKB5AEN X-Message-ID-Hash: 2RIN5Z3GY4NLHB73TL6CWSMZZRKB5AEN 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 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. 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. > 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. > Signed-off-by: David Gibson > --- > icmp.c | 16 ++++++---------- > 1 file changed, 6 insertions(+), 10 deletions(-) > > diff --git a/icmp.c b/icmp.c > index c745b7b..1f41440 100644 > --- a/icmp.c > +++ b/icmp.c > @@ -93,8 +93,7 @@ void icmp_sock_handler(const struct ctx *c, union epoll_ref ref) > icmp_id_map[V4][id].seq = seq; > } > > - debug("ICMP: echo %s to tap, ID: %i, seq: %i", > - (ih->type == ICMP_ECHO) ? "request" : "reply", id, seq); > + debug("ICMP: echo reply to tap, ID: %i, seq: %i", id, seq); > > tap_icmp4_send(c, sr.sin_addr, tap_ip4_daddr(c), buf, n); > } > @@ -138,8 +137,7 @@ void icmpv6_sock_handler(const struct ctx *c, union epoll_ref ref) > icmp_id_map[V6][id].seq = seq; > } > > - debug("ICMPv6: echo %s to tap, ID: %i, seq: %i", > - (ih->icmp6_type == 128) ? "request" : "reply", id, seq); > + debug("ICMPv6: echo reply to tap, ID: %i, seq: %i", id, seq); > > tap_icmp6_send(c, &sr.sin6_addr, > tap_ip6_daddr(c, &sr.sin6_addr), buf, n); > @@ -178,7 +176,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af, > if (!ih) > return 1; > > - if (ih->type != ICMP_ECHO && ih->type != ICMP_ECHOREPLY) > + if (ih->type != ICMP_ECHO) > return 1; > > iref.id = id = ntohs(ih->un.echo.id); > @@ -205,8 +203,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af, > (struct sockaddr *)&sa, sizeof(sa)) < 0) { > debug("ICMP: failed to relay request to socket"); > } else { > - debug("ICMP: echo %s to socket, ID: %i, seq: %i", > - (ih->type == ICMP_ECHO) ? "request" : "reply", > + debug("ICMP: echo request to socket, ID: %i, seq: %i", > id, ntohs(ih->un.echo.sequence)); > } > } else if (af == AF_INET6) { > @@ -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) > return 1; > > iref.id = id = ntohs(ih->icmp6_identifier); > @@ -249,8 +246,7 @@ int icmp_tap_handler(const struct ctx *c, uint8_t pif, int af, > (struct sockaddr *)&sa, sizeof(sa)) < 1) { > debug("ICMPv6: failed to relay request to socket"); > } else { > - debug("ICMPv6: echo %s to socket, ID: %i, seq: %i", > - (ih->icmp6_type == 128) ? "request" : "reply", > + debug("ICMPv6: echo request to socket, ID: %i, seq: %i", > id, ntohs(ih->icmp6_sequence)); > } > }