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>
That might just mean we shut down the socket -- but we still have to
go through the other states to ensure a orderly shutdown guest-side.
While at it, drop the EPOLLHUP check for unhandled states: we should
never hit that, but if we do, resetting the connection at that point
is probably the wrong thing to do.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Now that we dropped EPOLLET, we'll keep getting EPOLLRDHUP, and
possibly EPOLLIN, even if there's nothing to read anymore.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
EPOLLHUP just means we shut down one side of the connection on
*one* socket: remember, we have two sockets here.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...throughput isn't everything: this leads (of course) to horrible
latency with small, sparse messages. As a consequence, there's no
need to set TCP_NODELAY either.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If we're at the first message in a batch, it's safe to get the
window value from it, and there's no need to subtract anything for
a comparison on that's not even done -- we'll override it later in
any case if we find messages with a higher ACK sequence number.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...tcp_handler_splice() doesn't guarantee we read all the available
data, the sending buffer might be full.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Checking it only when the cached value is smaller than the current
window of the receiver is not enough: it might shrink further while
the receiver window is growing.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
If we couldn't write the whole batch of received packets to the socket,
and we have missing segments, we still need to request their
retransmission right away, otherwise it will take ages for the guest to
figure out we're missing them.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...instead of waiting for the remote peer to do that -- it's
especially important in case we request retransmissions from the
guest, but it also helps speeding up slow start. This should
probably be a configurable behaviour in the future.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Seen with iperf3: a control connection is established, no data flows
for a while, all segments are acknowledged. The socket starts closing
it, and we immediately time out because the last ACK from tap was one
minute before that.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Seen with iperf3: the first packet from socket (data connection) is
65520 bytes and doesn't fit in the window.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This fixes a number of issues found with some heavier testing with
uperf and neper:
- in most closing states, we can still accept data, check for EPOLLIN
when appropriate
- introduce a new state, ESTABLISHED_SOCK_FIN_SENT, to track the fact
we already sent a FIN segment to the tap device, for proper sequence
number bookkeeping
- for pasta mode only: spliced connections also need tracking of
(inferred) FIN segments and clean half-pipe shutdowns
- streamline resetting epoll_wait bitmaps with a new function,
tcp_tap_epoll_mask(), instead of repeating the logic all over the
place
- set EPOLLET for tap connections too, whenever we are waiting for
EPOLLRDHUP or an event from the tap to proceed with data transfer,
to avoid useless loops with EPOLLIN set
- impose an additional limit on the sending window advertised to the
guest, given by SO_SNDBUF: it makes no sense to completely fill
the sending buffer and send a zero window: stop a bit before we
hit that
- handle *all* interrupted system calls as needed
- simplify the logic for reordering of out-of-order segments received
from tap: it's not a corner case, and the previous logic allowed
for deadloops
- fix comparison of seen IPv4 address when we get a new connection
from a socket directed to the configured guest address
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>
As data from socket is forwarded to the guest, sendmmsg() might send
fewer bytes than requested in three different ways:
- failing altogether with a negative error code -- ignore that,
we'll get an error on the UNIX domain socket later if there's
really an issue with it and reset the connection to the guest
- sending less than 'vlen' messages -- instead of assuming success
in that case and waiting for the guest to send a duplicate ACK
indicating missing data, update the sequence number according to
what was actually sent and spare some retransmissions
- somewhat unexpectedly to me, sending 'vlen' or less than 'vlen'
messages, returning up to 'vlen', with the last message being
partially sent, and no further indication of errors other than
the returned msg_len for the last partially sent message being
less than iov_len.
In this case, we would assume success and proceed as nothing
happened. However, qemu would fail to parse any further message,
having received a partial descriptor, and eventually close the
connection, logging:
serious error: oversized packet received,connection terminated.
as the length descriptor for the next message would be sourced
from the middle of the next successfully sent message, not from
its header.
Handle this by checking the msg_len returned for the last (even
partially) sent message, and force re-sending the missing bytes,
if any, with a blocking sendmsg() -- qemu must not receive
anything else than that anyway.
While at it, allow to send up to 64KiB for each message, the
previous 32KiB limit isn't actually required, and just switch to a
new message at each iteration on sending buffers, they are already
MSS-sized anyway, so the check in the loop isn't really needed.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
With a kernel older than 5.3 (no_snd_wnd set), ack_pending in
tcp_send_to_tap() might be true at the beginning of a new connection
initiated by a socket. This means we send the first SYN segment to the
tap together with ACK set, which is clearly invalid and triggers the
receiver to reply with an RST segment right away.
Set ack_pending to 0 whenever we're sending a SYN segment. In case of a
SYN, ACK segment sent by the caller, the caller passes the ACK flag
explicitly.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Socket-facing functions don't guarantee that all data is handled before
they return: stick to level-triggered mode for TCP sockets.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
...and while at it, fix an issue in the calculation of the last IOV
buffer size: if we can't receive enough data to fill up the window,
the last buffer can be filled completely.
Also streamline the code setting iovec lengths if cached values are
not matching.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
We won't necessarily have another choice to ACK in a timely fashion
if we skip ACKs from a number of states (including ESTABLISHED) when
there's enough window left. Check for ACKed bytes as soon as it makes
sense.
If the sending window is not reported by the kernel, ACK as soon as
we queue onto the socket, given that we're forced to use a rather
small window.
In FIN_WAIT_1_SOCK_FIN, we also have to account for the FIN flag sent
by the peer in the sequence.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Sending 64 frames in a batch looks quite bad when a duplicate ACK
comes right at the beginning of it. Lowering this to 32 doesn't
affect performance noticeably, with 16 the impact is more apparent.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Similar to UDP, but using a simple sendmsg() on iovec-style buffers
from tap instead, as we don't need to preserve message boundaries.
A quick test in PASTA mode, from namespace to init via tap:
# ip link set dev pasta0 mtu 16384
# iperf3 -c 192.168.1.222 -t 60
[...]
[ ID] Interval Transfer Bitrate
[ 5] 0.00-60.00 sec 80.4 GBytes 11.5 Gbits/sec receiver
# iperf3 -c 2a02:6d40:3cfc:3a01:2b20:4a6a:c25a:3056 -t 60
[...]
[ ID] Interval Transfer Bitrate
[ 5] 0.00-60.01 sec 39.9 GBytes 5.71 Gbits/sec receiver
# ip link set dev pasta0 mtu 65520
# iperf3 -c 192.168.1.222 -t 60
[...]
[ ID] Interval Transfer Bitrate
[ 5] 0.00-60.01 sec 88.7 GBytes 12.7 Gbits/sec receiver
# iperf3 -c 2a02:6d40:3cfc:3a01:2b20:4a6a:c25a:3056 -t 60
[...]
[ ID] Interval Transfer Bitrate
[ 5] 0.00-60.00 sec 79.5 GBytes 11.4 Gbits/sec receiver
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
There's no need to constantly query the socket for number of
acknowledged bytes if we're far from exhausting the sending window,
just do it if we're at least down to 90% of it.
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>
This isn't optional: TCP streams must carry a unique, hard-to-guess,
non-zero label for each direction. Linux, probably among others,
will otherwise refuse to associate packets in a given stream to the
same connection.
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>
...not just for loopback addresses, with the address of the default
gateway. Otherwise, the guest might receive packets with source and
destination set to the same address.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This is actually reasonable in terms of memory consumption and
allows for better performance with local services.
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>
Before commit 8f7baad7f035 ("tcp: Add snd_wnd to TCP_INFO"), the
kernel didn't export tcpi_snd_wnd via TCP_INFO, which means we don't
know what's the window size of the receiver, socket-side.
To get TCP connections working in that case, ignore this value if
it's zero during handshake, and use the initial window value as
suggested by RFC 6928 (14 600 bytes, instead of 4 380 bytes), to
keep network performance usable.
To make the TCP dynamic responsive enough in this case, also check
the socket for available data whenever we get an ACK segment from
tap, instead of waiting until all the data from the tap is dequeued.
While at it, fix the window scaling value sent for SYN and SYN, ACK
segments: we want to increase the data pointer after writing the
option, not the value itself.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
During handshake, the initial SYN, ACK segment to the guest, send as
a response to the SYN segment, needs to report the unscaled value for
the window, given that the handshake hasn't completed yet.
While at it, fix the endianness for the window value in case TCP
parameters can't be queried via TCP_INFO and we need to use the
default value.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
and, given that the connection table is indexed by socket number,
we also need to increase MAX_CONNS now as the ICMP implementation
needs 2^17 sockets, that will be opened before TCP connections are
accepted.
This needs to be changed later: the connection table should be
indexed by a translated number -- we're wasting 2^17 table entries
otherwise. Move initialisation of TCP listening sockets as last
per-protocol initialisation, this will make it easier.
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
