Currently we set NLBUFSIZ large enough for 8192 netlink headers (128kiB in
total), and reference netlink(7). However netlink(7) says nothing about
reponse buffer sizes, and the documents which do reference 8192 *bytes* not
8192 headers.
Update NLBUFSIZ to 64kiB with a more detailed rationale.
Link: https://bugs.passt.top/show_bug.cgi?id=67
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
So far we never checked for errors reported on netlink operations via
NLMSG_ERROR messages. This has led to several subtle and tricky to debug
situations which would have been obvious if we knew that certain netlink
operations had failed.
Introduce a nl_do() helper that performs netlink "do" operations (that is
making a single change without retreiving complex information) with much
more thorough error checking. As well as returning an error code if we
get an NLMSG_ERROR message, we also check for unexpected behaviour in
several places. That way if we've made a mistake in our assumptions about
how netlink works it should result in a clear error rather than some subtle
misbehaviour.
We update those calls to nl_req() that can use the new wrapper to do so.
We will extend those to better handle errors in future. We don't touch
non-"do" operations for now, those are a bit trickier.
Link: https://bugs.passt.top/show_bug.cgi?id=60
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently netlink functions need to fill in a full netlink header, as well
as a payload then call nl_req() to submit that to the kernel. It makes
things a bit terser if we just give the relevant header fields as
parameters to nl_req() and have it complete the header.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Errors on send() or recv() calls on a netlink socket don't indicate errors
with the netlink operations we're attempting, but rather that something's
gone wrong with the mechanics of netlink itself. We don't really expect
this to ever happen, and if it does, it's not clear what we could to to
recover.
So, treat errors from these calls as fatal, rather than returning the error
up the stack. This makes handling failures in the callers of nl_req()
simpler.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Netlink messages have a sequence number that's used to match requests to
responses. It mostly doesn't matter what it is as long as it monotonically
increases, so we just use a global counter which we advance with each
request.
However, we start this counter at 0, so our very first request has sequence
number 0, which is usually reserved for asynchronous messages from the
kernel which aren't in response to a specific request. Since we don't (for
now) use such async messages, this doesn't really matter, but it's not
good practce. So start the sequence at 1 instead.
Link: https://bugs.passt.top/show_bug.cgi?id=67
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
nl_req() is designed to handle a single netlink request message: it only
receives a single reply datagram for the request, and only waits for a
single NLMSG_DONE or NLMSG_ERROR message at the beginning to clear out
things from previous requests.
However, in both nl_addr_dup() and nl_route_dup() we can send multiple
request messages as a single datagram, with a single nl_req() call.
This can easily mean that the replies nl_req() collects get out of
sync with requests. We only get away with this because after we call
these functions we don't make any netlink calls where we need to parse
the replies.
This is fragile, so alter nl_*_dup() to make an nl_req() call for each
address it is adding in the target namespace.
For nl_route_dup() this fixes an additional minor problem: because
routes can have dependencies, some of the route add requests might
fail on the first attempt, so we need to repeat the requests a number
of times. When we did that, we weren't updating the sequence number
on each new attempt. This works, but not updating the sequence number
for each new request isn't ideal. Now that we're making the requests
one at a time, it's easier to make sure we update the sequence number
each time.
Link: https://bugs.passt.top/show_bug.cgi?id=67
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
All the netlink operations currently implicitly use one of the two global
netlink sockets, sometimes depending on an 'ns' parameter. Change them
all to explicitly take the socket to use (or two sockets to use in the case
of the *_dup() functions). As well as making these functions strictly more
general, it makes the callers easier to follow because we're passing a
socket variable with a name rather than an unexplained '0' or '1' for the
ns parameter.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Minor formatting changes in pasta_ns_conf()]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This improves consistency with IPv6 and makes it harder to misuse these as
some other sort of value.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
nl_route() can perform 3 quite different operations based on the 'op'
parameter. Split this into separate functions for each one. This requires
more lines of code, but makes the internal logic of each operation much
easier to follow.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
nl_addr() can perform three quite different operations based on the 'op'
parameter, each of which uses a different subset of the parameters. Split
them up into a function for each operation. This does use more lines of
code, but the overlap wasn't that great, and the separated logic is much
easier to follow.
It's also clearer in the callers what we expect the netlink operations to
do, and what information it uses.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Minor formatting fixes in pasta_ns_conf()]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
nl_link() performs a number of functions: it can bring links up, set MAC
address and MTU and also retrieve the existing MAC. This makes for a small
number of lines of code, but high conceptual complexity: it's quite hard
to follow what's going on both in nl_link() itself and it's also not very
obvious which function its callers are intending to use.
Clarify this, by splitting nl_link() into nl_link_up(), nl_link_set_mac(),
and nl_link_get_mac(). The first brings up a link, optionally setting the
MTU, the others get or set the MAC address.
This fixes an arguable bug in pasta_ns_conf(): it looks as though that was
intended to retrieve the guest MAC whether or not c->pasta_conf_ns is set.
However, it only actually does so in the !c->pasta_conf_ns case: the fact
that we set up==1 means we would only ever set, never get, the MAC in the
nl_link() call in the other path. We get away with this because the MAC
will quickly be discovered once we receive packets on the tap interface.
Still, it's neater to always get the MAC address here.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
tap_ns_tun(), which runs in an ephemeral thread puts the fd it opens into
the global variable tun_ns_fd to communicate it back to the main thread
in tap_sock_tun_init().
However, the only thing tap_sock_tun_init() does with it is copies it to
c->fd_tap and everything else uses it from there. tap_ns_tun() already
has access to the context structure, so we might as well store the value
directly in there rather than having a global as an intermediate.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
There are several possible failure points in tap_ns_tun(), but if anything
goes wrong, we just set tun_ns_fd to -1 resulting in the same error
message.
Add more detailed error reporting to the various failure points. At the
same time, we know this is only called from tap_sock_tun_init() which will
terminate pasta if we fail, so we can simplify things a little because we
don't need to close() the fd on the failure paths.
Link: https://bugs.passt.top/show_bug.cgi?id=69
Link: https://github.com/containers/podman/issues/19428
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
ns_enter() returns an integer... but it's always zero. If we actually fail
the function doesn't return. Therefore it makes more sense for this to be
a function returning void, and we can remove the cases where we pointlessly
checked its return value.
In addition ns_enter() is usually called from an ephemeral thread created
by NS_CALL(). That means that the exit(EXIT_FAILURE) there usually won't
be reported (since NS_CALL() doesn't wait() for the thread). So, use die()
instead to print out some information in the unlikely event that our
setns() here does fail.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
union epoll_ref is used to subdivide the 64-bit data field in struct
epoll_event. Thus it *must* fit within that field or we're likely to get
very subtle and nasty bugs. C11 introduces the notion of static assertions
which we can use to verify this is the case at compile time.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
union epoll_ref has a deeply nested set of structs and unions to let us
subdivide it into the various different fields we want. This means that
referencing elements can involve an awkward long string of intermediate
fields.
Using C11 anonymous structs and unions lets us do this less clumsily.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
C11 has some features that will allow us to make some things a bit cleaner.
Alter the Makefile to tell the compiler to allow us to use C11 code.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This reverts commit cc2a6bec3c: I
applied that patch by mistake.
Fixes: cc2a6bec3c ("MAKE: Fix parallel builds; .o files; .gitignore; new makedocs")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We don't handle defragmentation of IP packets coming from the tap side,
and we're unlikely to any time soon (with our large MTU, it's not useful
for practical use cases). Currently, however, we simply ignore the
fragmentation flags and treat fragments as though they were whole IP
packets. This isn't ideal and can lead to rather cryptic behaviour if we
do receive IP fragments.
Change the code to explicitly drop fragmented packets, and print a rate
limited warning if we do encounter them.
Link: https://bugs.passt.top/show_bug.cgi?id=62
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
When interface names are specified in forwarding specs, we need to check
the length of the given interface name against the limit of IFNAMSIZ - 1
(15) characters. However, we managed to have 3 separate off-by-one errors
here meaning we only accepted interface names up to 12 characters.
1. At the point of the check 'ifname' was still on the '%' character, not
the first character of the name, meaning we overestimated the length by
one
2. At the point of the check 'spec' had been advanced one character past
the '/' which terminates the interface name, meaning we overestimated
the length by another one
3. We checked if the (miscalculated) length was >= IFNAMSIZ - 1, that is
>= 15, whereas lengths equal to 15 should be accepted.
Correct all 3 errors.
Link: https://bugs.passt.top/show_bug.cgi?id=61
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Network interface names must fit in a buffer of IFNAMSIZ bytes, including
the terminating \0. IFNAMSIZ is 16 on Linux, so interface names can be
up to (and including) 15 characters long.
We validate this for the -I option, but we have an off by one error. We
pass (IFNAMSIZ - 1) as the buffer size to snprintf(), but that buffer size
already includes the terminating \0, so this actually truncates the value
to 14 characters. The return value returned from snprintf() however, is
the number of characters that would have been printed *excluding* the
terminating \0, so by comparing it >= IFNAMSIZ - 1 we are giving an error
on names >= 15 characters rather than strictly > 15 characters.
Link: https://bugs.passt.top/show_bug.cgi?id=61
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
nl_addr() and nl_route() take an 'op' selector which affects a number of
parameters to the netlink call. Unfortunately when we introduced this
option a bug was introduced so that we always use the interface index for
the host side, rather than the one for the pasta namespace.
Really, the entire interface to nl_addr() and nl_route() is pretty bad:
it's tightly coupled with the use cases of its callers. This is a minimal
fix which doesn't address that, but also doesn't make it significantly
worse.
Link: https://bugs.passt.top/show_bug.cgi?id=59
Fixes: 2fe0461856 ("netlink: Add functionality to copy routes from outer namespace")
Fixes: e89da3cf03 ("netlink: Add functionality to copy addresses from outer namespace")
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
When the open() or setns() calls fails pasta exits early and prints an
error. However it did not include the errno so it was impossible to know
why the syscall failed.
Signed-off-by: Paul Holzinger <pholzing@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Split print to fit 80 columns in pasta_open_ns()]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
When pasta is started from an existing userns and tries to join the
netns from another process it fails to open /proc/$pid/ns/net due the
missing CAP_SYS_PTRACE capability in the --netns-only case.
A simple reproducer for this.
First create a userns:
$ unshare -r
Then create a new netns inside it and try to join that netns with pasta.
$ unshare -n sleep inf &
$ pasta --config-net --netns /proc/$!/ns/net
Signed-off-by: Paul Holzinger <pholzing@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
While --no-copy-addrs and --no-copy-routes only make sense with
--config-net, and they are implied on -g and -a, respectively, that
doesn't mean we should refuse -a or -g without --config-net: they are
still relevant for a number of things (including DHCP/DHCPv6/NDP
configuration).
Reported-by: Gianluca Stivan <me@yawnt.com>
Fixes: cc9d16758b ("conf, pasta: With --config-net, copy all addresses by default")
Fixes: da54641f14 ("conf, pasta: With --config-net, copy all routes by default")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
I wrote it in commit message and man page, but not in conf()...
Note that -g/--gateway correctly implies --no-copy-routes already.
This fixes Podman's tests:
podman networking with pasta(1) - IPv4 address assignment
podman networking with pasta(1) - IPv4 default route assignment
where we pass -a and -g to assign an address and a default gateway
that's compatible with it, but -a doesn't disable the copy of
addresses, so we ignore -a, and the default gateway is incompatible
with the addresses we copy -- hence no routes in the container.
Link: https://github.com/containers/podman/pull/18612
Fixes: cc9d16758b ("conf, pasta: With --config-net, copy all addresses by default")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
seccomp.sh generates seccomp.h piece by piece using >> directives. This
means that if two instances of seccomp.h are run concurrently a corrupted
version of seccomp.h will be generated. Amongst other problems this can
cause spurious failures on clang-tidy.
Alter seccomp.sh to build the output in a temporary file and atomic move it
to seccomp.h, so concurrent invocations will still result in valud output.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Erik suggests that this makes it easier to grep for options, and with
--help we're anyway printing usage information as expected, not as
part of an error report.
While at it: on -h, we should exit with 0.
Reported-by: Erik Sjölund <erik.sjolund@gmail.com>
Link: https://bugs.passt.top/show_bug.cgi?id=52
Link: https://bugs.passt.top/show_bug.cgi?id=53
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Since commit 0515adceaa ("passt, pasta: Namespace-based sandboxing,
defer seccomp policy application"), it makes no sense to close and
reopen the tap device on error: we don't have access to /dev/net/tun
after the initial setup phase.
If we hit ENOBUFS while writing (as reported: in one case because
the kernel actually ran out of memory, with another case under
investigation), or ENOSPC, we're supposed to drop whatever data we
were trying to send: there's no room for it.
Handle EINTR just like we handled EAGAIN/EWOULDBLOCK: there's no
particular reason why sending the same data should fail again.
Anything else I can think of would be an unrecoverable error: exit
with failure then.
While at it, drop a useless cast on the write() call: it takes a
const void * anyway.
Reported-by: Gianluca Stivan <me@yawnt.com>
Reported-by: Chris Kuhn <kuhnchris@kuhnchris.eu>
Fixes: 0515adceaa ("passt, pasta: Namespace-based sandboxing, defer seccomp policy application")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
a7359f0948 ("conf: Don't exit if sourced default route has no gateway")
was supposed to allow passt/pasta to run even if given a template interface
which has no default gateway. However a mistake in the patch means it
still requires the gateway, but doesn't require a global address for the
guest which we really do need.
This is one part (but not the only part) of the problem seen in
https://bugs.passt.top/show_bug.cgi?id=50.
Reported-by: Justin Jereza <justinjereza@gmail.com>
Fixes: a7359f0948 ("conf: Don't exit if sourced default route has no gateway")
Link: https://bugs.passt.top/show_bug.cgi?id=50
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
nstool loops on accept(), but failed to close the accepted socket fds
before continuing on. So, with repeated commands it would eventually die
with an EMFILE.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Normal filesystem paths can be very long (PATH_MAX is around 8k), however
Unix domain sockets can only use relatively short paths (UNIX_PATH_MAX is
108 on Linux). Currently nstool will simply truncate paths that are too
long, leading to difficult to understand failures.
Make such failures clearer, with an explicit error message if given a path
that's too long.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Use the newly-introduced NL_DUP mode for nl_addr() to copy all the
addresses associated to the template interface in the outer
namespace, unless --no-copy-addrs (also implied by -a) is given.
This option is introduced as deprecated right away: it's not expected
to be of any use, but it's helpful to keep it around for a while to
debug any suspected issue with this change.
This is done mostly for consistency with routes. It might partially
cover the issue at:
https://bugs.passt.top/show_bug.cgi?id=47
Support multiple addresses per address family
for some use cases, but not the originally intended one: we'll still
use a single outbound address (unless the routing table specifies
different preferred source addresses depending on the destination),
regardless of the address used in the target namespace.
Link: https://bugs.passt.top/show_bug.cgi?id=47
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Similarly to what we've just done with routes, support NL_DUP for
addresses (currently not exposed): nl_addr() can optionally copy
mulitple addresses to the target namespace, by fixing up data from
the dump with appropriate flags and interface index, and repeating
it back to the kernel on the socket opened in the target namespace.
Link-local addresses are not copied: the family is set to AF_UNSPEC,
which means the kernel will ignore them. Same for addresses from a
mismatching address (pre-4.19 kernels without support for
NETLINK_GET_STRICT_CHK).
Ignore IFA_LABEL attributes by changing their type to IFA_UNSPEC,
because in general they will report mismatching names, and we don't
really need to use labels as we already know the interface index.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
If we use a template interface without a gateway on the default
route, we can still offer almost complete functionality, except that,
of course, we can't map the gateway address to the outer namespace or
host, and that we have no obvious server address or identifier for
use in DHCP's siaddr and option 54 (Server identifier, mandatory).
Continue, if we have a default route but no default gateway, and
imply --no-map-gw and --no-dhcp in that case. NDP responder and
DHCPv6 should be able to work as usual because we require a
link-local address to be present, and we'll fall back to that.
Together with the previous commits implementing an actual copy of
routes from the outer namespace, this should finally fix the
operation of 'pasta --config-net' for cases where we have a default
route on the host, but no default gateway, as it's the case for
tap-style routes, including typical Wireguard endpoints.
Reported-by: me@yawnt.com
Link: https://bugs.passt.top/show_bug.cgi?id=49
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
This reverts commit 7656a6f888: now, by
default, we copy all the routes associated to the outbound interface
into the routing table of the container, so there's no need for this
horrible workaround anymore.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Use the newly-introduced NL_DUP mode for nl_route() to copy all the
routes associated to the template interface in the outer namespace,
unless --no-copy-routes (also implied by -g) is given.
This option is introduced as deprecated right away: it's not expected
to be of any use, but it's helpful to keep it around for a while to
debug any suspected issue with this change.
Otherwise, we can't use default gateways which are not, address-wise,
on the same subnet as the container, as reported by Callum.
Reported-by: Callum Parsey <callum@neoninteger.au>
Link: https://github.com/containers/podman/issues/18539
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Instead of just fetching the default gateway and configuring a single
equivalent route in the target namespace, on 'pasta --config-net', it
might be desirable in some cases to copy the whole set of routes
corresponding to a given output interface.
For instance, in:
https://github.com/containers/podman/issues/18539
IPv4 Default Route Does Not Propagate to Pasta Containers on Hetzner VPSes
configuring the default gateway won't work without a gateway-less
route (specifying the output interface only), because the default
gateway is, somewhat dubiously, not on the same subnet as the
container.
This is a similar case to the one covered by commit 7656a6f888
("conf: Adjust netmask on mismatch between IPv4 address/netmask and
gateway"), and I'm not exactly proud of that workaround.
We also have:
https://bugs.passt.top/show_bug.cgi?id=49
pasta does not work with tap-style interface
for which, eventually, we should be able to configure a gateway-less
route in the target namespace.
Introduce different operation modes for nl_route(), including a new
NL_DUP one, not exposed yet, which simply parrots back to the kernel
the route dump for a given interface from the outer namespace, fixing
up flags and interface indices on the way, and requesting to add the
same routes in the target namespace, on the interface we manage.
For n routes we want to duplicate, send n identical netlink requests
including the full dump: routes might depend on each other and the
kernel processes RTM_NEWROUTE messages sequentially, not atomically,
and repeating the full dump naturally resolves dependencies without
the need to actually calculate them.
I'm not kidding, it actually works pretty well.
Link: https://github.com/containers/podman/issues/18539
Link: https://bugs.passt.top/show_bug.cgi?id=49
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
In pasta_wait_for_ns(), open() failing with ENOENT is expected: we're
busy-looping until the network namespace appears. But any other
failure is not something we're going to recover from: return right
away if we don't get either success or ENOENT.
Now that pasta_wait_for_ns() can actually fail, handle that in
pasta_start_ns() by reporting the issue and exiting.
Looping on EPERM, when pasta doesn't actually have the permissions to
join a given namespace, isn't exactly a productive thing to do.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If pasta spawns a child process while running as UID 0, which is only
allowed from a non-init namespace, we need to keep CAP_SETFCAP before
pasta_start_ns() is called: otherwise, starting from Linux 5.12, we
won't be able to update /proc/self/uid_map with the intended mapping
(from 0 to 0). See user_namespaces(7).
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
If we want /proc contents to be consistent after pasta spawns a child
process in a new PID namespace (only for operation without a
pre-existing namespace), we need to mount /proc after the clone(2)
call with CLONE_NEWPID, and we enable the child to do that by
passing, in the same call, the CLONE_NEWNS flag, as described by
pid_namespaces(7).
This is not really a remount: in fact, passing MS_REMOUNT to mount(2)
would make the call fail. We're in another mount namespace now, so
it's a fresh mount that has the effect of hiding the existing one.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
We'll need this in isolate_initial(). While at it, don't rely on
BUFSIZ: the earlier issue we had with musl reminded me it's not a
magic "everything will fit" value. Size the read buffer to what we
actually need from uid_map, and check for the final newline too,
because uid_map is organised in lines.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
When we receive packets from the tap side, we update the addr_seen fields
to reflect the last known address of the guest or ns. For ip4.addr_seen
we, sensibly, only update if the address we've just seen isn't 0 (0.0.0.0).
This case can occur during early DHCP transactions.
We have no equivalent case for IPv6. We're less likely to hit this,
because DHCPv6 uses link-local addresses, however we can see an source
address of :: with certain multicast operations. This can bite us if we
try to make an incoming connection very early after starting pasta with
--config-net: we may have only seen some of those multicast packets,
updated addr_seen to :: and not had any "real" packets to update it to a
global address. I've seen this with some of the avocado test conversions.
In any case, it can never make sense to update addr_seen to ::, so
explicitly exclude that case.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Valtteri reports that if SIGPIPE already has a disposition set by the
parent process, such as systemd with the default setting of
IgnoreSIGPIPE=yes, signal() will return the previous value, not zero,
and this is not an error: check for SIG_ERR instead.
While at it, split messages for failures of sigaction() and signal(),
and report the actual error.
Reported-by: Valtteri Vuorikoski <vuori@notcom.org>
Fixes: 8534be076c ("Catch failures when installing signal handlers")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If we enter a mount namespace with nstool exec our working directory will
be changed to / in the new mount ns. This is surprising if we haven't
actually altered any mounts yet in the new ns. Instead, change the working
directory to match that of the holder process in this situation.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
