When using the new SO_PEEK_OFF feature on TCP sockets, we must adjust
the SO_PEEK_OFF value whenever we move conn->seq_to_tap backwards.
Although it was discussed during development, somewhere during the shuffles
the case where we move the pointer backwards because we lost frames while
sending them to the guest. This can happen, for example, if the socket
buffer on the Unix socket to qemu overflows.
Fixing this is slightly complicated because we need to pass a non-const
context pointer to some places we previously didn't need it. While we're
there also fix a small stylistic issue in the function comment for
tcp_revert_seq() - it was using spaces instead of tabs.
Fixes: e63d281871 ("tcp: leverage support of SO_PEEK_OFF socket option when available")
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Stefano Brivio <sbrivio@redhat.com>
Currently we always deliver inbound TCP packets to the guest's most
recent observed IP address. This has the odd side effect that if the
guest changes its IP address with active TCP connections we might
deliver packets from old connections to the new address. That won't
work; it will probably result in an RST from the guest. Worse, if the
guest added a new address but also retains the old one, then we could
break those old connections by redirecting them to the new address.
Now that we maintain flowside information, we have a record of the correct
guest side address and can just use it.
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
>From linux-6.9.0 the kernel will contain
commit 05ea491641d3 ("tcp: add support for SO_PEEK_OFF socket option").
This new feature makes is possible to call recv_msg(MSG_PEEK) and make
it start reading data from a given offset set by the SO_PEEK_OFF socket
option. This way, we can avoid repeated reading of already read bytes of
a received message, hence saving read cycles when forwarding TCP
messages in the host->name space direction.
In this commit, we add functionality to leverage this feature when
available, while we fall back to the previous behavior when not.
Measurements with iperf3 shows that throughput increases with 15-20
percent in the host->namespace direction when this feature is used.
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
As we are going to introduce the MODE_VU that will act like
the mode MODE_PASST, compare to MODE_PASTA rather than to add
a comparison to MODE_VU when we check for MODE_PASST.
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Move all the TCP parts using internal buffers to tcp_buf.c
and keep generic TCP management functions in tcp.c.
Add tcp_internal.h to export needed functions from tcp.c and
tcp_buf.h from tcp_buf.c
With this change we can use existing TCP functions with a
different kind of memory storage as for instance the shared
memory provided by the guest via vhost-user.
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
