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[2a10:fc81:a806:d6a9::1]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-435696fbea8sm2644686f8f.0.2026.01.15.19.44.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Jan 2026 19:44:56 -0800 (PST) Date: Fri, 16 Jan 2026 04:44:54 +0100 From: Stefano Brivio To: Yumei Huang Subject: Re: [PATCH v2] conf, pasta: Add --splice-only option Message-ID: <20260116044454.3da0958a@elisabeth> In-Reply-To: <20260116032509.1480589-1-yuhuang@redhat.com> References: <20260116032509.1480589-1-yuhuang@redhat.com> Organization: Red Hat X-Mailer: Claws Mail 4.2.0 (GTK 3.24.49; x86_64-pc-linux-gnu) MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: GFUdvGIsDcM2sGZvJDm300bBqiM9W6Mp-4hiWROp3N0_1768535098 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Message-ID-Hash: K2WJX3VCFBRUPL6NXFJDQQ2AM5AOVXTN X-Message-ID-Hash: K2WJX3VCFBRUPL6NXFJDQQ2AM5AOVXTN 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, david@gibson.dropbear.id.au 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 Fri, 16 Jan 2026 11:25:09 +0800 Yumei Huang wrote: > This patch introduces a mode where we only forward loopback connections > and traffic between two namespaces (via the loopback interface, 'lo'), > without a tap device. > > It might be used to fix up podman IPv4 / IPv6 loopback mapping when using > rootlesskit for forwarding ports, or a way to implement isolated containers. > > In this mode, --host-lo-to-ns-lo and --no-icmp are automatically enabled. > Option --no-splice is rejected. > > Link: https://bugs.passt.top/show_bug.cgi?id=149 > Signed-off-by: Yumei Huang > --- > conf.c | 39 ++++++++++++++++++++++++++++----------- > fwd.c | 3 +++ > passt.1 | 5 +++++ > passt.h | 2 ++ > pasta.c | 3 +++ > tap.c | 11 +++++++---- > 6 files changed, 48 insertions(+), 15 deletions(-) > > diff --git a/conf.c b/conf.c > index dbff87c..9d88ad7 100644 > --- a/conf.c > +++ b/conf.c > @@ -1059,7 +1059,8 @@ pasta_opts: > " --no-copy-addrs DEPRECATED:\n" > " Don't copy all addresses to namespace\n" > " --ns-mac-addr ADDR Set MAC address on tap interface\n" > - " --no-splice Disable inbound socket splicing\n"); > + " --no-splice Disable inbound socket splicing\n" > + " --splice-only Only enable loopback forwarding\n"); > > passt_exit(status); > } > @@ -1142,7 +1143,7 @@ static void conf_print(const struct ctx *c) > inet_ntop(AF_INET6, &c->ip6.addr_out, buf6, sizeof(buf6))); > } > > - if (c->mode == MODE_PASTA) > + if (c->mode == MODE_PASTA && !c->splice_only) > info("Namespace interface: %s", c->pasta_ifn); > > info("MAC:"); Actually, I just realised, also the MAC address information printed here is meaningless for the --splice-only mode: $ ./pasta --debug --splice-only 0.0019: MAC: 0.0019: host: 9a:55:9a:55:9a:55 ...but that MAC address will never appear anywhere. But in any case the patch looks good to me (with or without that "fixed"). -- Stefano