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0070e35d2b
Reflect the changes from commit 4b2e018d70 ("Allow different
external interfaces for IPv4 and IPv6 connectivity") into the manual.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
831 lines
29 KiB
Groff
831 lines
29 KiB
Groff
.\" SPDX-License-Identifier: AGPL-3.0-or-later
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.\" Copyright (c) 2020-2022 Red Hat GmbH
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.\" Author: Stefano Brivio <sbrivio@redhat.com>
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.TH passt 1
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.SH NAME
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.B passt
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\- Unprivileged user-mode network connectivity for virtual machines
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.br
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.B pasta
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\- Unprivileged user-mode network connectivity for network namespaces
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.SH SYNOPSIS
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.B passt
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[\fIOPTION\fR]...
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.br
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.B pasta
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[\fIOPTION\fR]... [\fIPID\fR|\fIPATH\fR|\fINAME\fR]
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.SH DESCRIPTION
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.SS passt
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.B passt
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(\fIP\fRlug \fIA\fR \fIS\fRimple \fIS\fRocket \fIT\fRransport) provides full,
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quasi-native network connectivity to virtual machines in user-mode without
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requiring any capabilities or privileges.
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The data plane implements a translation layer between a Layer-2 virtual network
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interface and native Layer-4 (TCP, UDP, ping) sockets on the host, giving the
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illusion that application processes residing on the guest are running on the
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local host, from a networking perspective.
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Built-in ARP, DHCP, NDP, and DHCPv6 implementations are designed to provide the
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guest with a network configuration that tightly resembles the host native
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configuration. With the default options, guest and host share IP addresses,
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routes, and port bindings.
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Port forwarding and translation allow networking services running in the guest
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to be reachable from both local and remote hosts.
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Unlike \fBslirp4netns\fR(1), \fBpasst\fR doesn't implement a full TCP stack: the
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TCP translation layer has no stateful data buffering and operates by reflecting
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one peer's observed parameters (congestion window size, acknowledged data, etc.)
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to the corresponding peer.
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Currently, the only supported hypervisor is \fBqemu\fR(1), connecting to
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\fBpasst\fR by means of a UNIX domain socket. This configuration can be obtained
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via out-of-tree qemu patches, available at:
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\fIhttps://passt.top/passt/tree/contrib/qemu\fR
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or with the \fBqrap\fR(1) wrapper.
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.SS pasta
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.B pasta
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(\fIP\fRack \fIA\fR \fIS\fRubtle \fIT\fRap \fIA\fRbstraction) provides
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equivalent functionality to network namespaces, as the one offered by
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\fBpasst\fR for virtual machines.
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If PID, PATH or NAME are given, \fBpasta\fR associates to an existing user and
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network namespace. Otherwise, \fBpasta\fR creates a new user and network
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namespace, and spawns an interactive shell within this context. A \fItap\fR
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device within the network namespace is created to provide network connectivity.
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For local TCP and UDP traffic only, \fBpasta\fR also implements a bypass path
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directly mapping Layer-4 sockets between \fIinit\fR and target namespaces,
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for performance reasons.
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.SH OPTIONS
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.TP
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.BR \-d ", " \-\-debug
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Be verbose, don't run in background.
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.TP
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.BR \-\-trace
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Be extra verbose, show single packets, don't run in background. Implies
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\fB--debug\fR.
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.TP
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.BR \-q ", " \-\-quiet
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Don't print informational messages.
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.TP
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.BR \-f ", " \-\-foreground
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Don't run in background. This implies that the process is not moved to a
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detached PID namespace after starting, because the PID itself cannot change.
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Default is to fork into background.
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.TP
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.BR \-e ", " \-\-stderr
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Log to standard error too.
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Default is to log to system logger only, if started from an interactive
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terminal, and to both system logger and standard error otherwise.
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.TP
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.BR \-\-runas " " \fIUID\fR|\fIUID:GID\fR|\fILOGIN\fR|\fILOGIN:GROUP\fR
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If started as root, change to given UID and corresponding group if UID is given,
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or to given UID and given GID if both are given. Alternatively, login name, or
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login name and group name can be passed.
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Default is to change to user \fInobody\fR if started as root.
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.TP
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.BR \-h ", " \-\-help
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Display a help message and exit.
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.TP
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.BR \-p ", " \-\-pcap " " \fIfile
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Capture tap-facing (that is, guest-side or namespace-side) network packets to
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\fIfile\fR in \fBpcap\fR format.
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If \fIfile\fR is not given, capture packets to
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\fB/tmp/passt_\fIISO8601-timestamp\fR_\fIPID\fB.pcap\fR
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in \fBpasst\fR mode and to
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\fB/tmp/pasta_\fIISO8601-timestamp\fR_\fIPID\fB.pcap\fR
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in \fBpasta\fR mode, where \fIPID\fR is the ID of the running process.
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.TP
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.BR \-P ", " \-\-pid " " \fIfile
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Write own PID to \fIfile\fR once initialisation is done, before forking to
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background (if configured to do so).
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.TP
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.BR \-m ", " \-\-mtu " " \fImtu
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Assign \fImtu\fR via DHCP (option 26) and NDP (option type 5).
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By default, no MTU options will be sent.
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.TP
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.BR \-a ", " \-\-address " " \fIaddr
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Assign IPv4 \fIaddr\fR via DHCP (\fByiaddr\fR), or \fIaddr\fR via DHCPv6 (option
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5) and an \fIaddr\fR-based prefix via NDP Router Advertisement (option type 3)
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for an IPv6 \fIaddr\fR.
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This option can be specified zero (for defaults) to two times (once for IPv4,
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once for IPv6).
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By default, assigned IPv4 and IPv6 addresses are taken from the host interfaces
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with the first default route for the corresponding IP version.
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.TP
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.BR \-n ", " \-\-netmask " " \fImask
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Assign IPv4 netmask \fImask\fR, expressed as dot-decimal or number of bits, via
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DHCP (option 1).
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By default, the netmask associated to the host address matching the assigned one
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is used. If there's no matching address on the host, the netmask is determined
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according to the CIDR block of the assigned address (RFC 4632).
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.TP
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.BR \-M ", " \-\-mac-addr " " \fIaddr
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Use source MAC address \fIaddr\fR when communicating to the guest or to the
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target namespace.
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Default is to use the MAC address of the interface with the first IPv4 default
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route on the host.
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.TP
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.BR \-g ", " \-\-gateway " " \fIaddr
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Assign IPv4 \fIaddr\fR as default gateway via DHCP (option 3), or IPv6
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\fIaddr\fR as source for NDP Router Advertisement and DHCPv6 messages.
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This option can be specified zero (for defaults) to two times (once for IPv4,
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once for IPv6).
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By default, IPv4 and IPv6 addresses are taken from the host interface with the
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first default route for the corresponding IP version.
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Note: these addresses are also used as source address for packets directed to
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the guest or to the target namespace having a loopback or local source address,
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to allow mapping of local traffic to guest and target namespace. See the
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\fBNOTES\fR below for more details about this mechanism.
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.TP
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.BR \-i ", " \-\-interface " " \fIname
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Use host interface \fIname\fR to derive addresses and routes.
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Default is to use the interfaces with the first default routes for each IP
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version.
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.TP
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.BR \-D ", " \-\-dns " " \fIaddr
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Use \fIaddr\fR (IPv4 or IPv6) for DHCP, DHCPv6, NDP or DNS forwarding, as
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configured (see options \fB--no-dhcp-dns\fR, \fB--dhcp-dns\fR,
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\fB--dns-forward\fR) instead of reading addresses from \fI/etc/resolv.conf\fR.
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This option can be specified multiple times, and a single, empty option disables
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usage of DNS addresses altogether.
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.TP
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.BR \-\-dns-forward " " \fIaddr
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Map \fIaddr\fR (IPv4 or IPv6) as seen from guest or namespace to the first
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configured DNS resolver (with corresponding IP version). Mapping is limited to
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UDP traffic directed to port 53, and DNS answers are translated back with a
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reverse mapping.
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This option can be specified zero to two times (once for IPv4, once for IPv6).
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.TP
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.BR \-S ", " \-\-search " " \fIlist
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Use space-separated \fIlist\fR for DHCP, DHCPv6, and NDP purposes, instead of
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reading entries from \fI/etc/resolv.conf\fR. See options \fB--no-dhcp-search\fR
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and \fB--dhcp-search\fR. A single, empty option disables the DNS domain search
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list altogether.
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.TP
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.BR \-\-no-dhcp-dns " " \fIaddr
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In \fIpasst\fR mode, do not assign IPv4 addresses via DHCP (option 23) or IPv6
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addresses via NDP Router Advertisement (option type 25) and DHCPv6 (option 23)
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as DNS resolvers.
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By default, all the configured addresses are passed.
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.TP
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.BR \-\-dhcp-dns " " \fIaddr
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In \fIpasta\fR mode, assign IPv4 addresses via DHCP (option 23) or IPv6
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addresses via NDP Router Advertisement (option type 25) and DHCPv6 (option 23)
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as DNS resolvers.
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By default, configured addresses, if any, are not passed.
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.TP
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.BR \-\-no-dhcp-search " " \fIaddr
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In \fIpasst\fR mode, do not send the DNS domain search list addresses via DHCP
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(option 119), via NDP Router Advertisement (option type 31) and DHCPv6 (option
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24).
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By default, the DNS domain search list resulting from configuration is passed.
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.TP
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.BR \-\-dhcp-search " " \fIaddr
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In \fIpasta\fR mode, send the DNS domain search list addresses via DHCP (option
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119), via NDP Router Advertisement (option type 31) and DHCPv6 (option 24).
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By default, the DNS domain search list resulting from configuration is not
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passed.
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.TP
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.BR \-\-no-tcp
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Disable the TCP protocol handler. No TCP connections will be accepted host-side,
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and TCP packets coming from guest or target namespace will be silently dropped.
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.TP
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.BR \-\-no-udp
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Disable the UDP protocol handler. No UDP traffic coming from the host side will
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be forwarded, and UDP packets coming from guest or target namespace will be
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silently dropped.
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.TP
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.BR \-\-no-icmp
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Disable the ICMP/ICMPv6 echo handler. ICMP and ICMPv6 echo requests coming from
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guest or target namespace will be silently dropped.
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.TP
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.BR \-\-no-dhcp
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Disable the DHCP server. DHCP client requests coming from guest or target
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namespace will be silently dropped.
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.TP
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.BR \-\-no-ndp
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Disable NDP responses. NDP messages coming from guest or target namespace will
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be ignored.
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.TP
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.BR \-\-no-dhcpv6
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Disable the DHCPv6 server. DHCPv6 client requests coming from guest or target
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namespace will be silently dropped.
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.TP
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.BR \-\-no-ra
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Disable Router Advertisements. Router Solicitations coming from guest or target
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namespace will be ignored.
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.TP
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.BR \-\-no-map-gw
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Don't remap TCP connections and untracked UDP traffic, with the gateway address
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as destination, to the host.
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.TP
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.BR \-4 ", " \-\-ipv4-only
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Enable IPv4-only operation. IPv6 traffic will be ignored.
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By default, IPv6 operation is enabled as long as at least an IPv6 default route
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and an interface address are configured on a given host interface.
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.TP
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.BR \-4 ", " \-\-ipv6-only
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Enable IPv6-only operation. IPv4 traffic will be ignored.
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By default, IPv4 operation is enabled as long as at least an IPv4 default route
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and an interface address are configured on a given host interface.
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.SS \fBpasst\fR-only options
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.TP
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.BR \-s ", " \-\-socket " " \fIpath
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Path for UNIX domain socket used by \fBqemu\fR(1) or \fBqrap\fR(1) to connect to
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\fBpasst\fR.
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Default is to probe a free socket, not accepting connections, starting from
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\fI/tmp/passt_1.socket\fR to \fI/tmp/passt_64.socket\fR.
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.TP
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.BR \-t ", " \-\-tcp-ports " " \fIspec
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Configure TCP port forwarding to guest. \fIspec\fR can be one of:
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.RS
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.TP
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.BR none
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Don't forward any ports
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.TP
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.BR all
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Forward all unbound, non-ephemeral ports, as permitted by current capabilities.
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For low (< 1024) ports, see \fBNOTES\fR.
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.TP
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.BR ports
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A comma-separated list of ports, optionally ranged with \fI-\fR, and,
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optionally, with target ports after \fI:\fR, if they differ. Specific addresses
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can be bound as well, separated by \fI/\fR. Within given ranges, selected ports
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and ranges can be excluded by an additional specification prefixed by \fI~\fR.
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Specifying excluded ranges only implies that all other ports are forwarded.
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Examples:
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.RS
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.TP
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-t 22
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Forward local port 22 to 22 on the guest
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.TP
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-t 22:23
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Forward local port 22 to port 23 on the guest
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.TP
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-t 22,25
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Forward local ports 22 and 25 to ports 22 and 25 on the guest
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.TP
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-t 22-80
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Forward local ports 22 to 80 to corresponding ports on the guest
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.TP
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-t 22-80-32:90
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Forward local ports 22 to 80 to corresponding ports on the guest plus 10
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.TP
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-t 192.0.2.1/22
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Forward local port 22, bound to 192.0.2.1, to port 22 on the guest
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.TP
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-t 2000-5000,~3000-3010
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Forward local ports 2000 to 5000, but not 3000 to 3010
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.TP
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-t 192.0.2.1/20-30,~25
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Forward local ports 20 to 24, and 26 to 30, bound to 192.0.2.1
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.TP
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-t ~20000-20010
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Forward all ports to the guest, except for the range from 20000 to 20010
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.RE
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Default is \fBnone\fR.
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.RE
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.TP
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.BR \-u ", " \-\-udp-ports " " \fIspec
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Configure UDP port forwarding to guest. \fIspec\fR is as described for TCP
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above.
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Note: unless overridden, UDP ports with numbers corresponding to forwarded TCP
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port numbers are forwarded too, without, however, any port translation. IPv6
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bound ports are also forwarded for IPv4.
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Default is \fBnone\fR.
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.SS \fBpasta\fR-only options
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.TP
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.BR \-I ", " \-\-ns-ifname " " \fIname
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Name of tap interface to be created in target namespace.
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By default, the same interface name as the external, routable interface is used.
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.TP
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.BR \-t ", " \-\-tcp-ports " " \fIspec
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Configure TCP port forwarding to namespace. \fIspec\fR can be one of:
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.RS
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.TP
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.BR none
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Don't forward any ports
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.TP
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.BR auto
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Dynamically forward ports bound in the namespace. The list of ports is
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periodically derived (every second) from listening sockets reported by
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\fI/proc/net/tcp\fR and \fI/proc/net/tcp6\fR, see \fBproc\fR(5).
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.TP
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.BR ports
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A comma-separated list of ports, optionally ranged with \fI-\fR, and,
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optionally, with target ports after \fI:\fR, if they differ. Specific addresses
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can be bound as well, separated by \fI/\fR. Within given ranges, selected ports
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and ranges can be excluded by an additional specification prefixed by \fI~\fR.
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Specifying excluded ranges only implies that all other ports are forwarded.
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Examples:
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.RS
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.TP
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-t 22
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Forward local port 22 to 22 in the target namespace
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.TP
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-t 22:23
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Forward local port 22 to port 23 in the target namespace
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.TP
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-t 22,25
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Forward local ports 22 and 25 to ports 22 and 25 in the target namespace
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.TP
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-t 22-80
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Forward local ports 22 to 80 to corresponding ports in the target namespace
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.TP
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-t 22-80-32:90
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Forward local ports 22 to 80 to corresponding ports plus 10 in the target
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namespace
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.TP
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-t 192.0.2.1/22
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Forward local port 22, bound to 192.0.2.1, to port 22 in the target namespace
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.TP
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-t 2000-5000,~3000-3010
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Forward local ports 2000 to 5000, but not 3000 to 3010
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.TP
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-t 192.0.2.1/20-30,~25
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Forward local ports 20 to 24, and 26 to 30, bound to 192.0.2.1
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.TP
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-t ~20000-20010
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Forward all ports to the namespace, except for the range from 20000 to 20010
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.RE
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IPv6 bound ports are also forwarded for IPv4.
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Default is \fBauto\fR.
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.RE
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.TP
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.BR \-u ", " \-\-udp-ports " " \fIspec
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Configure UDP port forwarding to namespace. \fIspec\fR is as described for TCP
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above, and the list of ports is derived from listening sockets reported by
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\fI/proc/net/udp\fR and \fI/proc/net/udp6\fR, see \fBproc\fR(5),
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when \fBpasta\fR starts (not periodically).
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Note: unless overridden, UDP ports with numbers corresponding to forwarded TCP
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port numbers are forwarded too, without, however, any port translation.
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IPv6 bound ports are also forwarded for IPv4.
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Default is \fBauto\fR.
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.TP
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.BR \-T ", " \-\-tcp-ns " " \fIspec
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Configure TCP port forwarding from target namespace to init namespace.
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\fIspec\fR is as described above for TCP.
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Default is \fBauto\fR.
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.TP
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.BR \-U ", " \-\-udp-ns " " \fIspec
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Configure UDP port forwarding from target namespace to init namespace.
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\fIspec\fR is as described above for UDP.
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Default is \fBauto\fR.
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.TP
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.BR \-\-userns " " \fIspec
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Target user namespace to join, as path or name (i.e. suffix for --nsrun-dir). If
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PID is given, without this option, the user namespace will be the one of the
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corresponding process.
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This option requires PID, PATH or NAME to be specified.
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.TP
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.BR \-\-netns-only
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Join only a target network namespace, not a user namespace, and don't create one
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for sandboxing purposes either. This is implied if PATH or NAME are given
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without \-\-userns.
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.TP
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.BR \-\-no-netns-quit
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If the target network namespace is bound to the filesystem (that is, if PATH or
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NAME are given as target), do not exit once the network namespace is deleted.
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.TP
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.BR \-\-nsrun-dir " " \fIpath
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Directory for nsfs mountpoints, used as path prefix for names of namespaces.
|
|
|
|
The default path is shown with --help.
|
|
|
|
.TP
|
|
.BR \-\-config-net
|
|
Configure networking in the namespace: set up addresses and routes as configured
|
|
or sourced from the host, and bring up the tap interface.
|
|
|
|
.TP
|
|
.BR \-\-ns-mac-addr " " \fIaddr
|
|
Configure MAC address \fIaddr\fR on the tap interface in the namespace.
|
|
|
|
Default is to let the tap driver build a pseudorandom hardware address.
|
|
|
|
.SH EXAMPLES
|
|
|
|
.SS \fBpasta
|
|
.BR "Create and use a new, connected, user and network namespace"
|
|
.RS
|
|
.nf
|
|
$ iperf3 -s -D
|
|
$ ./pasta
|
|
Outbound interface: eth0, namespace interface: eth0
|
|
ARP:
|
|
address: 28:16:ad:39:a9:ea
|
|
DHCP:
|
|
assign: 192.168.1.118
|
|
mask: 255.255.255.0
|
|
router: 192.168.1.1
|
|
NDP/DHCPv6:
|
|
assign: 2a02:6d40:3ca5:2001:b81d:fa4a:8cdd:cf17
|
|
router: fe80::62e3:27ff:fe33:2b01
|
|
#
|
|
# dhclient -4 --no-pid
|
|
# dhclient -6 --no-pid
|
|
# ip address show
|
|
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
|
|
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
|
|
inet 127.0.0.1/8 scope host lo
|
|
valid_lft forever preferred_lft forever
|
|
inet6 ::1/128 scope host
|
|
valid_lft forever preferred_lft forever
|
|
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 65520 qdisc pfifo_fast state UNKNOWN group default qlen 1000
|
|
link/ether 5e:90:02:eb:b0:2a brd ff:ff:ff:ff:ff:ff
|
|
inet 192.168.1.118/24 brd 192.168.1.255 scope global eth0
|
|
valid_lft forever preferred_lft forever
|
|
inet6 2a02:6d40:3ca5:2001:b81d:fa4a:8cdd:cf17/128 scope global
|
|
valid_lft forever preferred_lft forever
|
|
inet6 2a02:6d40:3ca5:2001:5c90:2ff:feeb:b02a/64 scope global dynamic mngtmpaddr
|
|
valid_lft 3591sec preferred_lft 3591sec
|
|
inet6 fe80::5c90:2ff:feeb:b02a/64 scope link
|
|
valid_lft forever preferred_lft forever
|
|
# ip route show
|
|
default via 192.168.1.1 dev eth0
|
|
192.168.1.0/24 dev eth0 proto kernel scope link src 192.168.1.118
|
|
# ip -6 route show
|
|
2a02:6d40:3ca5:2001:b81d:fa4a:8cdd:cf17 dev eth0 proto kernel metric 256 pref medium
|
|
2a02:6d40:3ca5:2001::/64 dev eth0 proto kernel metric 256 expires 3584sec pref medium
|
|
fe80::/64 dev eth0 proto kernel metric 256 pref medium
|
|
default via fe80::62e3:27ff:fe33:2b01 dev eth0 proto ra metric 1024 expires 3584sec pref medium
|
|
# iperf3 -c 127.0.0.1 -t1
|
|
Connecting to host 127.0.0.1, port 5201
|
|
[ 5] local 127.0.0.1 port 51938 connected to 127.0.0.1 port 5201
|
|
[ ID] Interval Transfer Bitrate Retr Cwnd
|
|
[ 5] 0.00-1.00 sec 4.46 GBytes 38.3 Gbits/sec 0 3.93 MBytes
|
|
- - - - - - - - - - - - - - - - - - - - - - - - -
|
|
[ ID] Interval Transfer Bitrate Retr
|
|
[ 5] 0.00-1.00 sec 4.46 GBytes 38.3 Gbits/sec 0 sender
|
|
[ 5] 0.00-1.41 sec 4.45 GBytes 27.1 Gbits/sec receiver
|
|
|
|
iperf Done.
|
|
# iperf3 -c ::1 -t1
|
|
Connecting to host ::1, port 5201
|
|
[ 5] local ::1 port 50108 connected to ::1 port 5201
|
|
[ ID] Interval Transfer Bitrate Retr Cwnd
|
|
[ 5] 0.00-1.00 sec 4.35 GBytes 37.4 Gbits/sec 0 4.99 MBytes
|
|
- - - - - - - - - - - - - - - - - - - - - - - - -
|
|
[ ID] Interval Transfer Bitrate Retr
|
|
[ 5] 0.00-1.00 sec 4.35 GBytes 37.4 Gbits/sec 0 sender
|
|
[ 5] 0.00-1.41 sec 4.35 GBytes 26.4 Gbits/sec receiver
|
|
|
|
iperf Done.
|
|
# ping -c1 -4 spaghetti.pizza
|
|
PING spaghetti.pizza (172.67.192.217) 56(84) bytes of data.
|
|
64 bytes from 172.67.192.217: icmp_seq=1 ttl=255 time=37.3 ms
|
|
|
|
--- spaghetti.pizza ping statistics ---
|
|
1 packets transmitted, 1 received, 0% packet loss, time 0ms
|
|
# ping -c1 -6 spaghetti.pizza
|
|
PING spaghetti.pizza(2606:4700:3034::6815:147a (2606:4700:3034::6815:147a)) 56 data bytes
|
|
64 bytes from 2606:4700:3034::6815:147a: icmp_seq=1 ttl=255 time=35.6 ms
|
|
|
|
--- spaghetti.pizza ping statistics ---
|
|
1 packets transmitted, 1 received, 0% packet loss, time 0ms
|
|
rtt min/avg/max/mdev = 35.605/35.605/35.605/0.000 ms
|
|
# logout
|
|
$
|
|
|
|
.RE
|
|
.fi
|
|
|
|
.BR "Connect an existing user and network namespace"
|
|
.RS
|
|
.nf
|
|
$ unshare -rUn
|
|
# echo $$
|
|
2446678
|
|
|
|
.fi
|
|
.BR " [From another terminal]"
|
|
.nf
|
|
$ ./pasta 2446678
|
|
Outbound interface: eth0, namespace interface: eth0
|
|
ARP:
|
|
address: 28:16:ad:39:a9:ea
|
|
DHCP:
|
|
assign: 192.168.1.118
|
|
mask: 255.255.255.0
|
|
router: 192.168.1.1
|
|
NDP/DHCPv6:
|
|
assign: 2a02:6d40:3ca5:2001:b81d:fa4a:8cdd:cf17
|
|
router: fe80::62e3:27ff:fe33:2b01
|
|
|
|
.fi
|
|
.BR " [Back to the original terminal]"
|
|
.nf
|
|
# dhclient -4 --no-pid
|
|
# dhclient -6 --no-pid
|
|
# ip address show
|
|
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
|
|
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
|
|
inet 127.0.0.1/8 scope host lo
|
|
valid_lft forever preferred_lft forever
|
|
inet6 ::1/128 scope host
|
|
valid_lft forever preferred_lft forever
|
|
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 65520 qdisc pfifo_fast state UNKNOWN group default qlen 1000
|
|
link/ether fa:c1:2a:27:92:a9 brd ff:ff:ff:ff:ff:ff
|
|
inet 192.168.1.118/24 brd 192.168.1.255 scope global eth0
|
|
valid_lft forever preferred_lft forever
|
|
inet6 2a02:6d40:3ca5:2001:b81d:fa4a:8cdd:cf17/128 scope global
|
|
valid_lft forever preferred_lft forever
|
|
inet6 2a02:6d40:3ca5:2001:f8c1:2aff:fe27:92a9/64 scope global dynamic mngtmpaddr
|
|
valid_lft 3594sec preferred_lft 3594sec
|
|
inet6 fe80::f8c1:2aff:fe27:92a9/64 scope link
|
|
valid_lft forever preferred_lft forever
|
|
.fi
|
|
.RE
|
|
|
|
.SS \fBpasst
|
|
.BR "Start and connect a guest with basic port forwarding"
|
|
.RS
|
|
.nf
|
|
$ ./passt -f -t 2222:22
|
|
Outbound interface: eth0
|
|
ARP:
|
|
address: 28:16:ad:39:a9:ea
|
|
DHCP:
|
|
assign: 192.168.1.118
|
|
mask: 255.255.255.0
|
|
router: 192.168.1.1
|
|
search:
|
|
redhat.com
|
|
NDP/DHCPv6:
|
|
assign: 2a02:6d40:3ca5:2001:b81d:fa4a:8cdd:cf17
|
|
router: fe80::62e3:27ff:fe33:2b01
|
|
search:
|
|
redhat.com
|
|
UNIX domain socket bound at /tmp/passt_1.socket
|
|
|
|
You can now start qrap:
|
|
./qrap 5 qemu-system-x86_64 ... -net socket,fd=5 -net nic,model=virtio
|
|
or directly qemu, patched with:
|
|
qemu/0001-net-Allow-also-UNIX-domain-sockets-to-be-used-as-net.patch
|
|
as follows:
|
|
qemu-system-x86_64 ... -net socket,connect=/tmp/passt_1.socket -net nic,model=virtio
|
|
|
|
.fi
|
|
.BR " [From another terminal]"
|
|
.nf
|
|
$ ./qrap 5 qemu-system-x86_64 test.qcow2 -m 1024 -display none -nodefaults -nographic -net socket,fd=5 -net nic,model=virtio
|
|
Connected to /tmp/passt_1.socket
|
|
|
|
.fi
|
|
.BR " [Back to the original terminal]"
|
|
.nf
|
|
passt: DHCP: ack to request
|
|
passt: from 52:54:00:12:34:56
|
|
passt: NDP: received NS, sending NA
|
|
passt: NDP: received RS, sending RA
|
|
passt: DHCPv6: received SOLICIT, sending ADVERTISE
|
|
passt: NDP: received NS, sending NA
|
|
passt: DHCPv6: received REQUEST/RENEW/CONFIRM, sending REPLY
|
|
passt: NDP: received NS, sending NA
|
|
|
|
.fi
|
|
.BR " [From yet another terminal]"
|
|
.nf
|
|
$ ssh -p 2222 root@localhost
|
|
root@localhost's password:
|
|
.fi
|
|
.BR " [...]"
|
|
.nf
|
|
# ip address show
|
|
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
|
|
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
|
|
inet 127.0.0.1/8 scope host lo
|
|
valid_lft forever preferred_lft forever
|
|
inet6 ::1/128 scope host
|
|
valid_lft forever preferred_lft forever
|
|
2: ens2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 65520 qdisc pfifo_fast state UP group default qlen 1000
|
|
link/ether 52:54:00:12:34:56 brd ff:ff:ff:ff:ff:ff
|
|
inet 192.168.1.118/24 brd 192.168.1.255 scope global noprefixroute ens2
|
|
valid_lft forever preferred_lft forever
|
|
inet6 2a02:6d40:3ca5:2001:b81d:fa4a:8cdd:cf17/128 scope global noprefixroute
|
|
valid_lft forever preferred_lft forever
|
|
inet6 2a02:6d40:3ca5:2001:b019:9ae2:a2fe:e6b4/64 scope global dynamic noprefixroute
|
|
valid_lft 3588sec preferred_lft 3588sec
|
|
inet6 fe80::1f98:d09f:9309:9e77/64 scope link noprefixroute
|
|
valid_lft forever preferred_lft forever
|
|
.fi
|
|
.RE
|
|
|
|
.SH NOTES
|
|
|
|
.SS Handling of traffic with local destination and source addressses
|
|
|
|
Both \fBpasst\fR and \fBpasta\fR can bind on ports with a local address,
|
|
depending on the configuration. Local destination or source addresses need to be
|
|
changed before packets are delivered to the guest or target namespace: most
|
|
operating systems would drop packets received from non-loopback interfaces with
|
|
local addresses, and it would also be impossible for guest or target namespace
|
|
to route answers back.
|
|
|
|
For convenience, and somewhat arbitrarily, the source address on these packets
|
|
is translated to the address of the default IPv4 or IPv6 gateway -- this is
|
|
known to be an existing, valid address on the same subnet.
|
|
|
|
Loopback destination addresses are instead translated to the observed external
|
|
address of the guest or target namespace. For IPv6 packets, if usage of a
|
|
link-local address by guest or namespace has ever been observed, and the
|
|
original destination address is also a link-local address, the observed
|
|
link-local address is used. Otherwise, the observed global address is used. For
|
|
both IPv4 and IPv6, if no addresses have been seen yet, the configured addresses
|
|
will be used instead.
|
|
|
|
For example, if \fBpasst\fR or \fBpasta\fR receive a connection from 127.0.0.1,
|
|
with destination 127.0.0.10, and the default IPv4 gateway is 192.0.2.1, while
|
|
the last observed source address from guest or namespace is 192.0.2.2, this will
|
|
be translated to a connection from 192.0.2.1 to 192.0.2.2.
|
|
|
|
Similarly, for traffic coming from guest or namespace, packets with destination
|
|
address corresponding to the default gateway will have their destination address
|
|
translated to a loopback address, if and only if a packet, in the opposite
|
|
direction, with a loopback destination or source address, port-wise matching for
|
|
UDP, or connection-wise for TCP, has been recently forwarded to guest or
|
|
namespace. This behaviour can be disabled with \-\-no\-map\-gw.
|
|
|
|
.SS Handling of local traffic in pasta
|
|
|
|
Depending on the configuration, \fBpasta\fR can bind to local ports in the init
|
|
namespace, in the target namespace, or both, and forward connections and packets
|
|
to corresponding ports in the other namespace.
|
|
|
|
To avoid unnecessary overhead, these connections and packets are not forwarded
|
|
through the tap device connecting the namespaces: \fBpasta\fR creates a socket
|
|
in the destination namespace, with matching Layer-4 protocol, and uses it to
|
|
forward local data. For TCP, data is forwarded between the originating socket
|
|
and the new socket using the \fBsplice\fR(2) system call, and for UDP, a pair
|
|
of \fBrecvmmsg\fR(2) and \fBsendmmsg\fR(2) system calls deals with packet
|
|
transfers.
|
|
|
|
This bypass only applies to local connections and traffic, because it's not
|
|
possible to bind sockets to foreign addresses.
|
|
|
|
.SS Binding to low numbered ports (well-known or system ports, up to 1023)
|
|
|
|
If the port forwarding configuration requires binding to port numbers lower than
|
|
1024, \fBpasst\fR and \fBpasta\fR will try to bind to them, but will fail if not
|
|
running as root, or without the \fICAP_NET_BIND_SERVICE\fR Linux capability, see
|
|
\fBservices\fR(5) and \fBcapabilities\fR(7). To grant the
|
|
\fICAP_NET_BIND_SERVICE\fR capability to passt, you can issue, as root:
|
|
|
|
.RS
|
|
setcap 'cap_net_bind_service=+ep' $(which passt)
|
|
.RE
|
|
|
|
.SS ICMP/ICMPv6 Echo sockets
|
|
|
|
ICMP and ICMPv6 Echo requests coming from guest or target namespace are handled
|
|
using so-called "ping" sockets, introduced in Linux 2.6.30. To preserve the
|
|
original identifier (see RFC 792, page 14, for ICMP, and RFC 4443, section 4.1,
|
|
for ICMPv6), \fBpasst\fR and \fBpasta\fR try to bind these sockets using the
|
|
observed source identifier as "port" -- that corresponds to Echo identifiers
|
|
for "ping" sockets.
|
|
|
|
As \fBbind\fR(2) failures were seen with particularly restrictive SELinux
|
|
policies, a fall-back mechanism maps different identifiers to different sockets,
|
|
and identifiers in replies will be mapped back to the original identifier of the
|
|
request. However, if \fBbind\fR(2) fails and the fall-back mechanism is used,
|
|
echo requests will be forwarded with different, albeit unique, identifiers.
|
|
|
|
For ICMP and ICMPv6 Echo requests to work, the \fIping_group_range\fR parameter
|
|
needs to include the PID of \fBpasst\fR or \fBpasta\fR, see \fBicmp\fR(7).
|
|
|
|
.SS pasta and loopback interface
|
|
|
|
As \fBpasta\fR connects to an existing namespace, or once it creates a new
|
|
namespace, it will also ensure that the loopback interface, \fIlo\fR, is brought
|
|
up. This is needed to bind ports using the loopback address in the namespace.
|
|
|
|
.SS TCP sending window and \fITCP_INFO\fB before Linux 5.3
|
|
|
|
To synchronise the TCP sending window from host Layer-4 sockets to the TCP
|
|
parameters announced in TCP segments sent over the Layer-2 interface,
|
|
\fBpasst\fR and \fBpasta\fR routinely query the size of the sending window seen
|
|
by the kernel on the corresponding socket using the \fITCP_INFO\fR socket
|
|
option, see \fBtcp\fR(7). Before Linux 5.3, i.e. before Linux kernel commit
|
|
8f7baad7f035 ("tcp: Add snd_wnd to TCP_INFO"), the sending window
|
|
(\fIsnd_wnd\fR field) is not available.
|
|
|
|
If the sending window cannot be queried, it will always be announced as the
|
|
current sending buffer size to guest or target namespace. This might affect
|
|
throughput of TCP connections.
|
|
|
|
.SH LIMITATIONS
|
|
|
|
Currently, IGMP/MLD proxying (RFC 4605) and support for SCTP (RFC 4960) are not
|
|
implemented.
|
|
|
|
TCP Selective Acknowledgment (RFC 2018), as well as Protection Against Wrapped
|
|
Sequences (PAWS) and Round-Trip Time Measurement (RTTM), both described by RFC
|
|
7232, are currently not implemented.
|
|
|
|
.SH AUTHOR
|
|
|
|
Stefano Brivio <sbrivio@redhat.com>
|
|
|
|
.SH REPORTING BUGS
|
|
|
|
Please report issues on the bug tracker at https://passt.top/passt/bugs, or
|
|
send a message to the passt-user@passt.top mailing list, see
|
|
https://passt.top/passt/lists.
|
|
|
|
.SH COPYRIGHT
|
|
|
|
Copyright (c) 2020-2022 Red Hat GmbH.
|
|
|
|
\fBpasst\fR and \fBpasta\fR are free software: you can redistribute them and/or
|
|
modify them under the terms of the GNU Affero General Public License as
|
|
published by the Free Software Foundation, either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
.SH SEE ALSO
|
|
|
|
\fBnamespaces\fR(7), \fBqemu\fR(1), \fBqrap\fR(1), \fBslirp4netns\fR(1).
|
|
|
|
High-level documentation is available at https://passt.top/passt/about/.
|