Update the UDP code to use the tap layer abstractions for initializing and
updating the L2 and lower headers. This will make adding other tap
backends in future easier.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We have separate IPv4 and IPv6 versions of a macro to construct an
initializer for ethernet headers. However, now that we have htons_constant
it's easy to simply paramterize this with the ethernet protocol number.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Both the TCP and UDP iov_init functions have some large structure literals
defined in "field order" style. These are pretty hard to read since it's
not obvious what value corresponds to what field. Use named field style
initializers instead to make this clearer.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently, when ports are forwarded inbound in pasta mode, we open two
sockets for incoming traffic: one listens on the public IP address and will
forward packets to the tuntap interface. The other listens on localhost
and forwards via "splicing" (resending directly via sockets in the ns).
Now that we've improved the logic about whether we "splice" any individual
packet, we don't need this. Instead we can have a single socket bound to
0.0.0.0 or ::, marked as able to splice and udp_sock_handler() will deal
with each packet as appropriate.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently we have special sockets for receiving datagrams from locahost
which can use the optimized "splice" path rather than going across the tap
interface.
We want to loosen this so that sockets can receive sockets that will be
forwarded by both the spliced and non-spliced paths. To do this, we alter
the meaning of the @splice bit in the reference to mean that packets
receieved on this socket *can* be spliced, not that they *will* be spliced.
They'll only actually be spliced if they come from 127.0.0.1 or ::1.
We can't (for now) remove the splice bit entirely, unlike with TCP. Our
gateway mapping means that if the ns initiates communication to the gw
address, we'll translate that to target 127.0.0.1 on the host side. Reply
packets will therefore have source address 127.0.0.1 when received on the
host, but these need to go via the tap path where that will be translated
back to the gateway address. We need the @splice bit to distinguish that
case from packets going from localhost to a port mapped explicitly with
-u which should be spliced.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
These two functions now have a very similar structure, and their first
part (calling recvmmsg()) is functionally identical. So, merge the two
functions into one.
This does have the side effect of meaning we no longer receive multiple
packets at once for splice (we already didn't for tap). This does hurt
throughput for small spliced packets, but improves it for large spliced
packets and tap packets.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
udp_splice_namebuf is now used only for spliced sending, and so it is
only ever populated with the localhost address, either IPv4 or IPv6.
So, replace the awkward initialization in udp_sock_handler_splice()
with statically initialized versions for IPv4 and IPv6. We then just
need to update the port number in udp_sock_handler_splice().
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
UDP_MAX_FRAMES gives the maximum number of datagrams we'll ever handle as a
batch for sizing our buffers and control structures. The subtly different
UDP_TAP_FRAMES gives the maximum number of datagrams we'll actually try to
receive at once for tap packets in the current configuration.
This depends on the mode, meaning that the macro has a non-obvious
dependency on the usual 'c' context variable being available. We only use
it in one place, so it makes more sense to open code this. Add an
explanatory comment while we're there.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The receive part of udp_sock_handler() and udp_sock_handler_splice() is now
almost identical. In preparation for merging that, split the receive part
of udp_sock_handler() from the part preparing and sending the frames for
sending on the tap interface. The latter goes into a new udp_tap_send()
function.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The last part of udp_sock_handler() does the actual sending of frames
to the tap interface. For pasta that's just a call to
udp_tap_send_pasta() but for passt, it's moderately complex and open
coded.
For symmetry, move the passt send path into its own function,
udp_tap_send_passt(). This will make it easier to abstract the tap
interface in future (e.g. when we want to add vhost-user).
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
udp_sock_handler() has a surprising difference in flow between pasta and
passt mode: For pasta we send each frame to the tap interface as we prepare
it. For passt, though, we prepare all the frames, then send them with a
single sendmmsg().
Alter the pasta path to also prepare all the frames, then send them at the
end. We already have a suitable data structure for the passt case. This
will make it easier to abstract out the tap backend difference in future.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The main purpose of udp_sock_fill_data_v[46]() is to construct the IP, UDP
and other headers we'll need to forward data onto the tap interface. In
addition they update the control structures (iovec and mmsghdr) we'll need
to send the messages, and in the case of pasta actually sends it.
This leads the control structure management and the send itself awkwardly
split between udp_sock_fill_data_v[46]() and their caller
udp_sock_handler(). In addition, this tail part of udp_sock_fill_datav[46]
is essentially common between the IPv4 and IPv6 versions, apart from which
control array we're working on.
Clean this up by reducing these functions to just construct the headers
and renaming them to udp_update_hdr[46]() accordingly. The control
structure updates are now all in the caller, and common for IPv4 and IPv6.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently, we always populate udp[46]_l2_iov_tap[].iov_base with the
very start of the header buffers, including space for the qemu vnet_len
tag suitable for passt mode. That's ok because we don't actually use these
iovecs for pasta mode.
However, we do know the mode in udp_sock[46]_iov_init() so adjust these
to the beginning of the headers we'll actually need for the mode: including
the vnet_len tag for passt, but excluding it for pasta.
This allows a slightly nicer way to locate the right buffer to send in the
pasta case, and will allow some additional cleanups later.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Apart from which mh array they're operating on the recvmmsg() calls in
udp_sock_handler() are identical between the IPv4 and IPv6 paths, as are
some of the control structure updates.
By using some local variables to refer to the IP version specific control
arrays, make some more logic common between the IPv4 and IPv6 paths. As
well as slightly reducing the code size, this makes it less likely that
we'll accidentally use the IPv4 arrays in the IPv6 path or vice versa as we
did in a recently fixed bug.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
udp_sock_handler() incorrectly uses udp6_l2_mh_tap[] on the IPv4 path. In
fact this is harmless because this assignment is redundant (the 0th entry
msg_hdr will always point to the 0th iov entry for both IPv4 and IPv6 and
won't change).
There is also an incorrect usage of udp6_l2_mh_tap[] in
udp_sock_fill_data_v4. This one can cause real problems, because we'll
use stale iov_len values if we send multiple messages to the qemu socket.
Most of the time that will be relatively harmless - we're likely to either
drop UDP packets, or send duplicates. However, if the stale iov_len we
use ends up referencing an uninitialized buffer we could desynchronize the
qemu stream socket.
Correct both these bugs. The UDP6 path appears to be correct, but it does
have some comments that incorrectly reference the IPv4 versions, so fix
those as well.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
udp_sock_handler_splice() reads a whole batch of datagrams at once with
recvmmsg(). It then forwards them all via a single socket on the other
side, based on the source port.
However, it's entirely possible that the datagrams in the set have
different source ports, and thus ought to be forwarded via different
sockets on the destination side. In fact this situation arises with the
iperf -P4 throughput tests in our own test suite. AFAICT we only get away
with this because iperf3 is strictly one way and doesn't send reply packets
which would be misdirected because of the incorrect source ports.
Alter udp_sock_handler_splice() to split the packets it receives into
batches with the same source address and send each batch with a separate
sendmmsg().
For now we only look for already contiguous batches, which means that if
there are multiple active flows interleaved this is likely to degenerate
to batches of size 1. For now this is the simplest way to correct the
behaviour and we can try to optimize later.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Move the part of udp_sock_handler_splice() concerned with sending out the
datagrams into a new udp_splice_sendfrom() helper. This will make later
cleanups easier.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We maintain a set of buffers for UDP packets to be forwarded via the tap
interface in udp[46]_l2_buf. We then have a separate set of buffers for
packets to be "spliced" in udp_splice_buf[]. However, we only use one of
these at a time, so we can share the buffer space.
For the receiving splice packets we can not only re-use the data buffers
but also the udp[46]_l2_iov_sock and udp[46]_l2_mh_sock control structures.
For sending the splice packets we keep the same data buffers, but we need
specific control structures. We create udp[46]_iov_splice - we can't
reuse udp_l2_iov_sock[] because we need to write iov_len as we're writing
spliced packets, but the tap path expects iov_len to remain the same (it
only uses it for receive). Likewise we create udp[46]_mh_splice with the
mmsghdr structures for sending spliced packets. As well as needing to
reference different iovs, these need to all reference udp_splice_namebuf
instead of individual msg_name fields for each slot.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
udp_sock_handler_splice() has a somewhat clunky if to extract the port from
a socket address which could be either IPv4 or IPv6. Future changes are
going to make this even more clunky, so introduce a helper function to
do this extraction.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
These two constants have the same value, and there's not a lot of reason
they'd ever need to be different. Future changes will further integrate
the spliced and "tap" paths so that these need to be the same. So, merge
them into UDP_MAX_FRAMES.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Previous cleanups mean that we can now rework some complex ifs in
udp_sock_handler_splice() into a simpler set.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
A UDP pseudo-connection between port A in the init namespace and port B in
the pasta guest namespace involves two sockets: udp_splice_init[v6][B]
and udp_splice_ns[v6][A]. The socket which originated this "connection"
will be permanent but the other one will be closed on a timeout.
When we get a packet from the originating socket, we update the timeout on
the other socket, but we don't do the same when we get a reply packet from
the other socket. However any activity on the "connection" probably
indicates that it's still in use. Without this we could incorrectly time
out a "connection" if it's using a protocol which involves a single
initiating packet, but which then gets continuing replies from the target.
Correct this by updating the timeout on both sockets for a packet in either
direction. This also updates the timestamps for the permanent originating
sockets which is unnecessary, but harmless.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
When we look up udp_splice_to_ns[][].orig_sock in udp_sock_handler_splice()
we're finding the socket on which the originating packet for the
"connection" was received on. However, we don't specifically need this
socket to be the originating one - we just need one that's bound to the
the source port of this reply packet in the init namespace. We can look
this up in udp_splice_to_init[v6][src].target_sock, whose defining
characteristic is exactly that. The same applies with init and ns swapped.
In practice, of course, the port we locate this way will always be the
originating port, since we couldn't have started this "connection" if it
wasn't.
Change this, and we no longer need the @orig_sock field at all. That
leaves just @target_sock which we rename to simply @sock. The whole
udp_splice_flow structure now more represents a single bound port than
a "flow" per se, so rename and recomment it accordingly. Likewise the
udp_splice_to_{ns,init} names are now misleading, since the ports in
those maps are used in both directions. Rename them to
udp_splice_{ns,init} indicating the location where the described
socket is bound.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
When we look up udp_splice_to_ns[v6][src].target_sock in
udp_sock_handler_splice, all we really require of the socket is that it
be bound to port src in the pasta guest namespace. Similarly for
udp_splice_to_init but bound in the init namespace.
Usually these sockets are created temporarily by udp_splice_connect() and
cleaned up by udp_timer(). However, depending on the -u and -U options its
possible we have a permanent socket bound to the relevant port created by
udp_sock_init(). If such a socket exists, we could use it instead of
creating a temporary one. In fact we *must* use it, because we'll fail
trying to bind() a temporary one to the same port.
So allow this, store permanently bound sockets into udp_splice_to_{ns,init}
in udp_sock_init(). These won't get incorrectly removed by the timer
because we don't put a corresponding entry in the udp_act[] structure
which directs the timer what to clean up.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
For each IP version udp_socket() has 3 possible calls to sock_l4(). One
is for the "non-spliced" bound socket in the init namespace, one for the
"spliced" bound socket in the init namespace and one for the "spliced"
bound socket in the pasta namespace.
However when this is called to create a socket in the pasta namspeace there
is a logic error which causes it to take the path for the init side spliced
socket as well as the ns socket. This essentially tries to create two
identical sockets on the ns side. Unsurprisingly the second bind() call
fails according to strace.
Correct this to only attempt to open one socket within the ns.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The @splice field in union udp_epoll_ref can have a number of values for
different types of "spliced" packet flows. Split it into several single
bit fields with more or less independent meanings. The new @splice field
is just a boolean indicating whether the socket is associated with a
spliced flow, making it identical to the @splice fiend in tcp_epoll_ref.
The new bit @orig, indicates whether this is a socket which can originate
new udp packet flows (created with -u or -U) or a socket created on the
fly to handle reply socket. @ns indicates whether the socket lives in the
init namespace or the pasta namespace.
Making these bits more orthogonal to each other will simplify some future
cleanups.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We set this field, but nothing ever checked it.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Currently we connect() the socket we use to forward spliced UDP flows.
However, we now only ever use sendto() rather than send() on this socket
so there's not actually any need to connect it. Don't do so.
Rename a number of things that referred to "connect" or "conn" since that
would now be misleading.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
udp_sock_handler_splice() has two different ways of sending out packets
once it has determined the correct destination socket. For the originating
sockets (which are not connected) it uses sendto() to specify a specific
address. For the forward socket (which is connected) we use send().
However we know the correct destination address even for the forward socket
we do also know the correct destination address. We can use this to use
sendto() instead of send(), removing the need for two different paths and
some staging data structures.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Each entry udp_splice_map[v6][N] keeps information about two essentially
unrelated packet flows. @ns_conn_sock, @ns_conn_ts and @init_bound_sock
track a packet flow from port N in the host init namespace to some other
port in the pasta namespace (the one @ns_conn_sock is connected to).
@init_conn_sock, @init_conn_ts and @ns_bound_sock track packet flow from
port N in the pasta namespace to some other port in the host init namespace
(the one @init_conn_sock is connected to).
Split udp_splice_map[][] into two separate tables for the two directions.
Each entry in each table is a 'struct udp_splice_flow' with @orig_sock
(previously the bound socket), @target_sock (previously the connected
socket) and @ts (the timeout for the target socket).
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
pasta handles "spliced" port forwarding by resending datagrams received on
a bound socket in the init namespace to a connected socket in the guest
namespace. This means there are actually three ports associated with each
"connection". First there's the source and destination ports of the
originating datagram. That's also the destination port of the forwarded
datagram, but the source port of the forwarded datagram is the kernel
allocated bound address of the connected socket.
However, by bind()ing as well as connect()ing the forwarding socket we can
choose the source port of the forwarded datagrams. By choosing it to match
the original source port we remove that surprising third port number and
no longer need to store port numbers in struct udp_splice_port.
As a bonus this means that the recipient of the packets will see the
original source port if they call getpeername(). This rarely matters, but
it can't hurt.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Given that we use just the first valid DNS resolver address
configured, or read from resolv.conf(5) on the host, to forward DNS
queries to, in case --dns-forward is used, we don't need to duplicate
dns[] to dns_send[]:
- rename dns_send[] back to dns[]: those are the resolvers we
advertise to the guest/container
- for forwarding purposes, instead of dns[], use a single field (for
each protocol version): dns_host
- and rename dns_fwd to dns_match, so that it's clear this is the
address we are matching DNS queries against, to decide if they need
to be forwarded
Suggested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
If we disable a given IP version automatically (no corresponding
default route on host) or administratively (--ipv4-only or
--ipv6-only options), we don't initialise related buffers and
services (DHCP for IPv4, NDP and DHCPv6 for IPv6). The "tap"
handlers will also ignore packets with a disabled IP version.
However, in commit 3c6ae62510 ("conf, tcp, udp: Allow address
specification for forwarded ports") I happily changed socket
initialisation functions to take AF_UNSPEC meaning "any enabled
IP version", but I forgot to add checks back for the "enabled"
part.
Reported by Paul: on a host without default IPv6 route, but IPv6
enabled, connect, using IPv6, to a port handled by pasta, which
tries to send data to a tap device without initialised buffers
for that IP version and exits because the resulting write() fails.
Simpler way to reproduce: pasta -6 and inbound IPv4 connection, or
pasta -4 and inbound IPv6 connection.
Reported-by: Paul Holzinger <pholzing@redhat.com>
Fixes: 3c6ae62510 ("conf, tcp, udp: Allow address specification for forwarded ports")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Now that we allow loopback DNS addresses to be used as targets for
forwarding, we need to check if DNS answers come from those targets,
before deciding to eventually remap traffic for local redirects.
Otherwise, the source address won't match the one configured as
forwarder, which means that the guest or the container will refuse
those responses.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We recently corrected some errors handling the endianness of IPv4
addresses. These are very easy errors to make since although we mostly
store them in network endianness, we sometimes need to manipulate them in
host endianness.
To reduce the chances of making such mistakes again, change to always using
a (struct in_addr) instead of a bare in_addr_t or uint32_t to store network
endian addresses. This makes it harder to accidentally do arithmetic or
comparisons on such addresses as if they were host endian.
We introduce a number of IN4_IS_ADDR_*() helpers to make it easier to
directly work with struct in_addr values. This has the additional benefit
of making the IPv4 and IPv6 paths more visually similar.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This macro checks if an IPv4 address is in the loopback network
(127.0.0.0/8). There are two places where we open code an identical check,
use the macro instead.
There are also a number of places we specifically exclude the loopback
address (127.0.0.1), but we should actually be excluding anything in the
loopback network. Change those sites to use the macro as well.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
First off, as we swap endianness for source ports in
udp_fill_data_v{4,6}(), we want host endianness, not network
endianness. It doesn't actually matter if we use htons() or ntohs()
here, but the current version is confusing.
In the IPv4 path, when we remap DNS answers, we already swapped the
endianness as needed for the source port: don't swap it again,
otherwise we'll not map DNS answers for IPv4.
In the IPv6 path, when we remap DNS answers, we want to check that
they came from our upstream DNS server, not the one configured via
--dns-forward (which doesn't even need to exist for this
functionality to work).
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Since kernel version 5.7, commit c427bfec18f2 ("net: core: enable
SO_BINDTODEVICE for non-root users"), we can bind sockets to
interfaces, if they haven't been bound yet (as in bind()).
Introduce an optional interface specification for forwarded ports,
prefixed by %, that can be passed together with an address.
Reported use case: running local services that use ports we want
to have externally forwarded:
https://github.com/containers/podman/issues/14425
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Logging to file is going to add some further complexity that we don't
want to squeeze into util.c.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Commit c318ffcb4c ("udp: Ignore bogus -Wstringop-overread for
write() from gcc 12.1") uses a gcc pragma to ignore a bogus warning,
which started appearing on gcc 12.1 (aarch64 and x86_64) due to:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103483
...but gcc 12.2 has the same issue. Not just that: if LTO is enabled,
the pragma itself is ignored (this wasn't the case with gcc 12.1),
because of:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80922
Drop the pragma, and assign a frame (in the networking sense) pointer
from the offset of the Ethernet header in the buffer, then pass it to
write() and pcap(), so that gcc doesn't obsess anymore with the fact
that an Ethernet header is 14 bytes and we're sending more than that.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Port numbers (for both TCP and UDP) are 16-bit, and so fit exactly into a
'short'. USHRT_MAX is therefore the maximum port number and this is widely
used in the code. Unfortunately, a lot of those places don't actually
want the maximum port number (USHRT_MAX == 65535), they want the total
number of ports (65536). This leads to a number of potentially nasty
consequences:
* We have buffer overruns on the port_fwd::delta array if we try to use
port 65535
* We have similar potential overruns for the tcp_sock_* arrays
* Interestingly udp_act had the correct size, but we can calculate it in
a more direct manner
* We have a logical overrun of the ports bitmap as well, although it will
just use an unused bit in the last byte so isnt harmful
* Many loops don't consider port 65535 (which does mitigate some but not
all of the buffer overruns above)
* In udp_invert_portmap() we incorrectly compute the reverse port
translation for return packets
Correct all these by using a new NUM_PORTS defined explicitly for this
purpose.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Port numbers are unsigned values, but we're storing them in (signed) int
variables in some places. This isn't actually harmful, because int is
large enough to hold the entire range of ports. However in places we don't
want to use an in_port_t (usually to avoid overflow on the last iteration
of a loop) it makes more conceptual sense to use an unsigned int. This will
also avoid some problems with later cleanups.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Now that we've delayed initialization of the UDP specific "reverse" map
until udp_init(), the only difference between the various 'remap' functions
used in conf_ports() is which array they target. So, simplify by open
coding the logic into conf_ports() with a pointer to the correct mapping
array.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Because it's connectionless, when mapping UDP ports we need, in addition
to the table of deltas for destination ports needed by TCP, we need an
inverted table to translate the source ports on return packets.
Currently we fill out the inverted table at the same time we construct the
main table in udp_remap_to_tap() and udp_remap_to_init(). However, we
don't use either table until after we've initialized UDP, so we can delay
the construction of the reverse table to udp_init(). This makes the
configuration more symmetric between TCP and UDP which will enable further
cleanups.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The configuration for how to forward ports in and out of the guest/ns is
divided between several different variables. For each connect direction
and protocol we have a mode in the udp/tcp context structure, a bitmap
of which ports to forward also in the context structure and an array of
deltas to apply if the outward facing and inward facing port numbers are
different. This last is a separate global variable, rather than being in
the context structure, for no particular reason. UDP also requires an
additional array which has the reverse mapping used for return packets.
Consolidate these into a re-used substructure in the context structure.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
udp_tap_handler() currently skips outbound packets if they have a payload
length of zero. This is not correct, since in a datagram protocol zero
length packets still have meaning.
Adjust this to correctly forward the zero-length packets by using a msghdr
with msg_iovlen == 0.
Bugzilla: https://bugs.passt.top/show_bug.cgi?id=19
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
In udp_tap_handler() the array of msghdr structures, mm[], is initialized
to zero. Since UIO_MAXIOV is 1024, this can be quite a large zero, which
is expensive if we only end up using a few of its entries. It also makes
it less obvious how we're setting all the control fields at the point we
actually invoke sendmmsg().
Rather than pre-initializing it, just initialize each element as we use it.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
The context structure contains a batch of fields specific to IPv4 and to
IPv6 connectivity. Split those out into a sub-structure.
This allows the conf_ip4() and conf_ip6() functions, which take the
entire context but touch very little of it, to be given more specific
parameters, making it clearer what it affects without stepping through the
code.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
After recent changes, conf_ip() now has essentially entirely disjoint paths
for IPv4 and IPv6 configuration. So, it's cleaner to split them out into
different functions conf_ip4() and conf_ip6().
Splitting these out also lets us make the interface a bit nicer, having
them return success or failure directly, rather than manipulating c->v4
and c->v6 to indicate success/failure of the two versions.
Since these functions may also initialize the interface index for each
protocol, it turns out we can then drop c->v4 and c->v6 entirely, replacing
tests on those with tests on whether c->ifi4 or c->ifi6 is non-zero (since
a 0 interface index is never valid).
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Whitespace fixes]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
With current OpenSUSE Tumbleweed on aarch64 (gcc-12-1.3.aarch64) and
on x86_64 (gcc-12-1.4.x86_64), but curiously not on armv7hl
(gcc-12-1.3.armv7hl), gcc warns about using the _pointer_ to the
802.3 header to write the whole frame to the tap descriptor:
reading between 62 and 4294967357 bytes from a region of size 14
which is bogus:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103483
Probably declaring udp_sock_fill_data_v{4,6}() as noinline would
"fix" this, but that's on the data path, so I'd rather not. Use
a gcc pragma instead.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This feature is available in slirp4netns but was missing in passt and
pasta.
Given that we don't do dynamic memory allocation, we need to bind
sockets while parsing port configuration. This means we need to
process all other options first, as they might affect addressing and
IP version support. It also implies a minor rework of how TCP and UDP
implementations bind sockets.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Not an actual issue due to how it's typically stored, but udp_act
can also be used for ports 65528-65535. Reported by Coverity.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
All instances were harmless, but it might be useful to have some
debug messages here and there. Reported by Coverity.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The existing sizes provide no measurable differences in throughput
and packet rates at this point. They were probably needed as batched
implementations were not complete, but they can be decreased quite a
bit now.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Implement a packet abstraction providing boundary and size checks
based on packet descriptors: packets stored in a buffer can be queued
into a pool (without storage of its own), and data can be retrieved
referring to an index in the pool, specifying offset and length.
Checks ensure data is not read outside the boundaries of buffer and
descriptors, and that packets added to a pool are within the buffer
range with valid offset and indices.
This implies a wider rework: usage of the "queueing" part of the
abstraction mostly affects tap_handler_{passt,pasta}() functions and
their callees, while the "fetching" part affects all the guest or tap
facing implementations: TCP, UDP, ICMP, ARP, NDP, DHCP and DHCPv6
handlers.
Suggested-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This should never happen, but there are no formal guarantees: ensure
socket numbers are below SOCKET_MAX.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
There's no value in keeping a separate timestamp for activity and for
aging of local binds, given that they have the same timeout. Reduce
that to a single timestamp, with a flag indicating the local bind.
Also use flags instead of separate int fields for loopback and
configured unicast address usage as source address.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...it became too hard to follow: split it off to
udp_sock_fill_data_v{4,6}.
While at it, use IN6_ARE_ADDR_EQUAL(a, b), courtesy of netinet/in.h,
instead of open-coded memcmp().
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
It's already implied by the fact they don't have "l2" in their
names, and dropping it improves readability a bit.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
In pasta mode, when we get data from sockets and write it as single
frames to the tap device, we batch receive operations considerably,
and then (conceptually) split the data in many smaller writes.
It looked like an obvious choice, but performance is actually better
if we receive data in many small frame-sized recvmsg()/recvmmsg().
The syscall overhead with the previous behaviour, observed by perf,
comes predominantly from write operations, but receiving data in
shorter chunks probably improves cache locality by a considerable
amount.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Likely for testing purposes only: allow connections from host to
guest or namespace using, as connection target, the configured,
possibly global unicast address.
In this case, we have to map the destination address to a link-local
address, and for port-based tracked responses, the source address
needs to be again the unicast address: not loopback, not link-local.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
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>
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>
Bitmap manipulating functions would otherwise refer to inconsistent
sets of bits on big-endian architectures. While at it, fix up a
couple of casts.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This is the only remaining Linux-specific include -- drop it to avoid
clang-tidy warnings and to make code more portable.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...mostly false positives, but a number of very relevant ones too,
in tcp_get_sndbuf(), tcp_conn_from_tap(), and siphash PREAMBLE().
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The issue with a higher UDP_TAP_FRAMES was actually coming from a
payload size the guest couldn't digest. Fix that, and bump
UDP_TAP_FRAMES back to 128.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Unions and structs, you all have names now.
Take the chance to enable bugprone-reserved-identifier,
cert-dcl37-c, and cert-dcl51-cpp checkers in clang-tidy.
Provide a ffsl() weak declaration using gcc built-in.
Start reordering includes, but that's not enough for the
llvm-include-order checker yet.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This shouldn't happen on any sane configuration, but I just met an
example of that: the default IPv6 gateway on the host is configured
with a global unicast address, we use that as source for RA, DHCPv6
replies, and the guest ignores it. Same later on if we talk TCP or
UDP and the guest has no idea where that address comes from.
Use our link-local address in case the gateway address is global.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
A mix of unchecked return values, a missing permission mask for
open(2) with O_CREAT, and some false positives from
-Wstringop-overflow and -Wmaybe-uninitialized.
Reported-by: Martin Hauke <mardnh@gmx.de>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
The 'ts' field is a timestamp so assigning the socket file descriptor is
incorrect. There is no actual bug because the current time is assigned
just a few lines later:
udp_tap_map[V4][src].sock = s;
udp_tap_map[V4][src].ts = s;
^^^^^^^^^^^ bogus ^^^^^^^^^^
bitmap_set(udp_act[V4][UDP_ACT_TAP], src);
}
udp_tap_map[V4][src].ts = now->tv_sec;
^^^^^^^^^^^^^^^ correct ^^^^^^^^^^^^^^
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
List of allowed syscalls comes from comments in the form:
#syscalls <list>
for syscalls needed both in passt and pasta mode, and:
#syscalls:pasta <list>
#syscalls:passt <list>
for syscalls specifically needed in pasta or passt mode only.
seccomp.sh builds a list of BPF statements from those comments,
prefixed by a binary search tree to keep lookup fast.
While at it, clean up a bit the Makefile using wildcards.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
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>
Until now, messages would be passed to protocol handlers in a single
batch only if they happened to be dequeued in a row. Packets
interleaved between different connections would result in multiple
calls to the same protocol handler for a single connection.
Instead, keep track of incoming packet descriptors, arrange them in
sequences, and call protocol handlers only as we completely sorted
input messages in batches.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Similarly to the decrease in TCP_TAP_FRAMES, this improves fairness,
with a very small impact on performance.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This went lost in a recent rework: if the guest wants to connect
directly to the host, it can use the address of the default gateway.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Similarly to the handling introduced by commit "tcp: Proper error
handling for sendmmsg() to UNIX domain socket" for TCP, we need to
deal with partial sendmmsg() failures for UDP as well.
Here, we can lose messages, but we need to make sure that the last
message is delivered completely, otherwise qemu will fail to
reassemble further packets. For UDP, this is somewhat complicated
by the fact that one message might include multiple datagrams, and
we need to respect message boundaries: go through headers, and
calculate what we need to re-send, if anything.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Traffic with loopback source address will be forwarded to the direct
loopback connection in the namespace, and the tap interface is used
for the rest.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Provide an AVX2-based function using compiler intrinsics for
TCP/IP-style checksums. The load/unpack/add idea and implementation
is largely based on code from BESS (the Berkeley Extensible Software
Switch) licensed as 3-Clause BSD, with a number of modifications to
further decrease pipeline stalls and to minimise cache pollution.
This speeds up considerably data paths from sockets to tap
interfaces, decreasing overhead for checksum computation, with
16-64KiB packet buffers, from approximately 11% to 7%. The rest is
just syscalls at this point.
While at it, provide convenience targets in the Makefile for avx2,
avx2_debug, and debug targets -- these simply add target-specific
CFLAGS to the build.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Allow to bind IPv4 and IPv6 ports to tap, namespace or init separately.
Port numbers of TCP ports that are bound in a namespace are also bound
for UDP for convenience (e.g. iperf3), and IPv4 ports are always bound
if the corresponding IPv6 port is bound (socket might not have the
IPV6_V6ONLY option set). This will also be configurable later.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Packets are received directly onto pre-cooked, static buffers
for IPv4 (with partial checksum pre-calculation) and IPv6 frames,
with pre-filled Ethernet addresses and, partially, IP headers,
and sent out from the same buffers with sendmmsg(), for both
passt and pasta (non-local traffic only) modes.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
PASTA (Pack A Subtle Tap Abstraction) provides quasi-native host
connectivity to an otherwise disconnected, unprivileged network
and user namespace, similarly to slirp4netns. Given that the
implementation is largely overlapping with PASST, no separate binary
is built: 'pasta' (and 'passt4netns' for clarity) both link to
'passt', and the mode of operation is selected depending on how the
binary is invoked. Usage example:
$ unshare -rUn
# echo $$
1871759
$ ./pasta 1871759 # From another terminal
# udhcpc -i pasta0 2>/dev/null
# ping -c1 pasta.pizza
PING pasta.pizza (64.190.62.111) 56(84) bytes of data.
64 bytes from 64.190.62.111 (64.190.62.111): icmp_seq=1 ttl=255 time=34.6 ms
--- pasta.pizza ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 34.575/34.575/34.575/0.000 ms
# ping -c1 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 (2606:4700:3034::6815:147a): icmp_seq=1 ttl=255 time=29.0 ms
--- spaghetti.pizza ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 28.967/28.967/28.967/0.000 ms
This entails a major rework, especially with regard to the storage of
tracked connections and to the semantics of epoll(7) references.
Indexing TCP and UDP bindings merely by socket proved to be
inflexible and unsuitable to handle different connection flows: pasta
also provides Layer-2 to Layer-2 socket mapping between init and a
separate namespace for local connections, using a pair of splice()
system calls for TCP, and a recvmmsg()/sendmmsg() pair for UDP local
bindings. For instance, building on the previous example:
# ip link set dev lo up
# iperf3 -s
$ iperf3 -c ::1 -Z -w 32M -l 1024k -P2 | tail -n4
[SUM] 0.00-10.00 sec 52.3 GBytes 44.9 Gbits/sec 283 sender
[SUM] 0.00-10.43 sec 52.3 GBytes 43.1 Gbits/sec receiver
iperf Done.
epoll(7) references now include a generic part in order to
demultiplex data to the relevant protocol handler, using 24
bits for the socket number, and an opaque portion reserved for
usage by the single protocol handlers, in order to track sockets
back to corresponding connections and bindings.
A number of fixes pertaining to TCP state machine and congestion
window handling are also included here.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This is in preparation for scatter-gather IO on the UDP receive path:
save a getsockname() syscall by setting a flag if we get the numbering
of all bound sockets in a strict sequence (expected, in practice) and
repurpose the tap buffer to be also a socket receive buffer, passing
it down to protocol handlers.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
As we support UDP forwarding for packets that are sent to local
ports, we actually need some kind of connection tracking for UDP.
While at it, this commit introduces a number of vaguely related fixes
for issues observed while trying this out. In detail:
- implement an explicit, albeit minimalistic, connection tracking
for UDP, to allow usage of ephemeral ports by the guest and by
the host at the same time, by binding them dynamically as needed,
and to allow mapping address changes for packets with a loopback
address as destination
- set the guest MAC address whenever we receive a packet from tap
instead of waiting for an ARP request, and set it to broadcast on
start, otherwise DHCPv6 might not work if all DHCPv6 requests time
out before the guest starts talking IPv4
- split context IPv6 address into address we assign, global or site
address seen on tap, and link-local address seen on tap, and make
sure we use the addresses we've seen as destination (link-local
choice depends on source address). Similarly, for IPv4, split into
address we assign and address we observe, and use the address we
observe as destination
- introduce a clock_gettime() syscall right after epoll_wait() wakes
up, so that we can remove all the other ones and pass the current
timestamp to tap and socket handlers -- this is additionally needed
by UDP to time out bindings to ephemeral ports and mappings between
loopback address and a local address
- rename sock_l4_add() to sock_l4(), no semantic changes intended
- include <arpa/inet.h> in passt.c before kernel headers so that we
can use <netinet/in.h> macros to check IPv6 address types, and
remove a duplicate <linux/ip.h> inclusion
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...on a second thought, this won't really help with veth, and
actually causes a significant overhead as we get EPOLLERR whenever
another process is tapping on the traffic.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Avoid a bunch of syscalls on forwarding paths by:
- storing minimum and maximum file descriptor numbers for each
protocol, fall back to SO_PROTOCOL query only on overlaps
- allocating a larger receive buffer -- this can result in more
coalesced packets than sendmmsg() can take (UIO_MAXIOV, i.e. 1024),
so make sure we don't exceed that within a single call to protocol
tap handlers
- nesting the handling loop in tap_handler() in the receive loop,
so that we have better chances of filling our receive buffer in
fewer calls
- skipping the recvfrom() in the UDP handler on EPOLLERR -- there's
nothing to be done in that case
and while at it:
- restore the 20ms timer interval for periodic (TCP) events, I
accidentally changed that to 100ms in an earlier commit
- attempt using SO_ZEROCOPY for UDP -- if it's not available,
sendmmsg() will succeed anyway
- fix the handling of the status code from sendmmsg(), if it fails,
we'll try to discard the first message, hence return 1 from the
UDP handler
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This is symmetric with tap operation and addressing model, and
allows again to reach the guest behind the tap interface by
contacting the local address.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Receive packets in batches from AF_UNIX, check if they can be sent
with a single syscall, and batch them up with sendmmsg() in case.
A bit rudimentary, currently only implemented for UDP, but it seems
to work.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
A bunch of fixes not worth single commits at this stage, notably:
- make buffer, length parameter ordering consistent in ARP, DHCP,
NDP handlers
- strict checking of buffer, message and option length in DHCP
handler (a malicious client could have easily crashed it)
- set up forwarding for IPv4 and IPv6, and masquerading with nft for
IPv4, from demo script
- get rid of separate slow and fast timers, we don't save any
overhead that way
- stricter checking of buffer lengths as passed to tap handlers
- proper dequeuing from qemu socket back-end: I accidentally trashed
messages that were bundled up together in a single tap read
operation -- the length header tells us what's the size of the next
frame, but there's no apparent limit to the number of messages we
get with one single receive
- rework some bits of the TCP state machine, now passive and active
connection closes appear to be robust -- introduce a new
FIN_WAIT_1_SOCK_FIN state indicating a FIN_WAIT_1 with a FIN flag
from socket
- streamline TCP option parsing routine
- track TCP state changes to stderr (this is temporary, proper
debugging and syslogging support pending)
- observe that multiplying a number by four might very well change
its value, and this happens to be the case for the data offset
from the TCP header as we check if it's the same as the total
length to find out if it's a duplicated ACK segment
- recent estimates suggest that the duration of a millisecond is
closer to a million nanoseconds than a thousand of them, this
trend is now reflected into the timespec_diff_ms() convenience
routine
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This is a reimplementation, partially building on the earlier draft,
that uses L4 sockets (SOCK_DGRAM, SOCK_STREAM) instead of SOCK_RAW,
providing L4-L2 translation functionality without requiring any
security capability.
Conceptually, this follows the design presented at:
https://gitlab.com/abologna/kubevirt-and-kvm/-/blob/master/Networking.md
The most significant novelty here comes from TCP and UDP translation
layers. In particular, the TCP state and translation logic follows
the intent of being minimalistic, without reimplementing a full TCP
stack in either direction, and synchronising as much as possible the
TCP dynamic and flows between guest and host kernel.
Another important introduction concerns addressing, port translation
and forwarding. The Layer 4 implementations now attempt to bind on
all unbound ports, in order to forward connections in a transparent
way.
While at it:
- the qemu 'tap' back-end can't be used as-is by qrap anymore,
because of explicit checks now introduced in qemu to ensure that
the corresponding file descriptor is actually a tap device. For
this reason, qrap now operates on a 'socket' back-end type,
accounting for and building the additional header reporting
frame length
- provide a demo script that sets up namespaces, addresses and
routes, and starts the daemon. A virtual machine started in the
network namespace, wrapped by qrap, will now directly interface
with passt and communicate using Layer 4 sockets provided by the
host kernel.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
