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* conf, udp: Introduce basic DNS forwardingStefano Brivio2022-02-211-10/+53
| | | | | | | | | | | | | | | | | | | | | | | | | For compatibility with libslirp/slirp4netns users: introduce a mechanism to map, in the UDP routines, an address facing guest or namespace to the first IPv4 or IPv6 address resulting from configuration as resolver. This can be enabled with the new --dns-forward option. This implies that sourcing and using DNS addresses and search lists, passed via command line or read from /etc/resolv.conf, is not bound anymore to DHCP/DHCPv6/NDP usage: for example, pasta users might just want to use addresses from /etc/resolv.conf as mapping target, while not passing DNS options via DHCP. Reflect this in all the involved code paths by differentiating DHCP/DHCPv6/NDP usage from DNS configuration per se, and in the new options --dhcp-dns, --dhcp-search for pasta, and --no-dhcp-dns, --no-dhcp-search for passt. This should be the last bit to enable substantial compatibility between slirp4netns.sh and slirp4netns(1): pass the --dns-forward option from the script too. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* passt, pasta: Namespace-based sandboxing, defer seccomp policy applicationStefano Brivio2022-02-211-7/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | To reach (at least) a conceptually equivalent security level as implemented by --enable-sandbox in slirp4netns, we need to create a new mount namespace and pivot_root() into a new (empty) mountpoint, so that passt and pasta can't access any filesystem resource after initialisation. While at it, also detach IPC, PID (only for passt, to prevent vulnerabilities based on the knowledge of a target PID), and UTS namespaces. With this approach, if we apply the seccomp filters right after the configuration step, the number of allowed syscalls grows further. To prevent this, defer the application of seccomp policies after the initialisation phase, before the main loop, that's where we expect bad things to happen, potentially. This way, we get back to 22 allowed syscalls for passt and 34 for pasta, on x86_64. While at it, move #syscalls notes to specific code paths wherever it conceptually makes sense. We have to open all the file handles we'll ever need before sandboxing: - the packet capture file can only be opened once, drop instance numbers from the default path and use the (pre-sandbox) PID instead - /proc/net/tcp{,v6} and /proc/net/udp{,v6}, for automatic detection of bound ports in pasta mode, are now opened only once, before sandboxing, and their handles are stored in the execution context - the UNIX domain socket for passt is also bound only once, before sandboxing: to reject clients after the first one, instead of closing the listening socket, keep it open, accept and immediately discard new connection if we already have a valid one Clarify the (unchanged) behaviour for --netns-only in the man page. To actually make passt and pasta processes run in a separate PID namespace, we need to unshare(CLONE_NEWPID) before forking to background (if configured to do so). Introduce a small daemon() implementation, __daemon(), that additionally saves the PID file before forking. While running in foreground, the process itself can't move to a new PID namespace (a process can't change the notion of its own PID): mention that in the man page. For some reason, fork() in a detached PID namespace causes SIGTERM and SIGQUIT to be ignored, even if the handler is still reported as SIG_DFL: add a signal handler that just exits. We can now drop most of the pasta_child_handler() implementation, that took care of terminating all processes running in the same namespace, if pasta started a shell: the shell itself is now the init process in that namespace, and all children will terminate once the init process exits. Issuing 'echo $$' in a detached PID namespace won't return the actual namespace PID as seen from the init namespace: adapt demo and test setup scripts to reflect that. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* passt: Fork into background also if not running from a terminalStefano Brivio2021-10-211-1/+1
| | | | | | | | | This is actually annoying: there's no way to make it fork into background when running from a script. However, it's always possible to keep it in foreground with -f. Make it simpler, and always fork into background if -f is not given. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* LICENSES: Add license text files, add missing notices, fix SPDX tagsStefano Brivio2021-10-201-0/+3
| | | | | | | | | | SPDX tags don't replace license files. Some notices were missing and some tags were not according to the SPDX specification, too. Now reuse --lint from the REUSE tool (https://reuse.software/) passes. Reported-by: Martin Hauke <mardnh@gmx.de> Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* conf: Add -P, --pid, to specify a file where own PID is written toStefano Brivio2021-10-141-0/+5
| | | | Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* conf, tcp, udp: Add --no-map-gw to disable mapping gateway address to hostStefano Brivio2021-10-141-1/+6
| | | | Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* doc: Add to man page tip to grant passt the CAP_NET_BIND_SERVICE capabilityStefano Brivio2021-10-141-1/+6
| | | | Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* doc: Fix up note about missing tcpi_snd_wnd in man pageStefano Brivio2021-10-141-7/+3
| | | | | | | | The behaviour without tcpi_snd_wnd changed: the only difference now is the advertised window, which corresponds to the queried sending buffer size. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* conf, tap: Split netlink and pasta functions, allow interface configurationStefano Brivio2021-10-141-0/+11
| | | | | | | | | | Move netlink routines to their own file, and use netlink to configure or fetch all the information we need, except for the TUNSETIFF ioctl. Move pasta-specific functions to their own file as well, add parameters and calls to configure the tap interface in the namespace. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* pasta: Allow specifying paths and names of namespacesGiuseppe Scrivano2021-10-071-6/+24
| | | | | | | | | | | | | | | | | | Based on a patch from Giuseppe Scrivano, this adds the ability to: - specify paths and names of target namespaces to join, instead of a PID, also for user namespaces, with --userns - request to join or create a network namespace only, without entering or creating a user namespace, with --netns-only - specify the base directory for netns mountpoints, with --nsrun-dir Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com> [sbrivio: reworked logic to actually join the given namespaces when they're not created, implemented --netns-only and --nsrun-dir, updated pasta demo script and man page] Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* conf, tcp: Periodic detection of bound ports for pasta port forwardingStefano Brivio2021-09-271-7/+8
| | | | | | | | | | Detecting bound ports at start-up time isn't terribly useful: do this periodically instead, if configured. This is only implemented for TCP at the moment, UDP is somewhat more complicated: leave a TODO there. Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
* passt, qrap: Add man pagesStefano Brivio2021-09-011-0/+707
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>