linux.git/include/linux/tcp.h, branch v3.9-rc2

tcp: adding a per-socket timestamp offset

2013-02-13T18:22:15+00:00

This functionality is used for restoring tcp sockets. A tcp timestamp
depends on how long a system has been running, so it's differ for each
host. The solution is to set a per-socket offset.

A per-socket offset for a TIME_WAIT socket is inherited from a proper
tcp socket.

tcp_request_sock doesn't have a timestamp offset, because the repair
mode for them are not implemented.

Cc: "David S. Miller" 
Cc: Alexey Kuznetsov 
Cc: James Morris 
Cc: Hideaki YOSHIFUJI 
Cc: Patrick McHardy 
Cc: Eric Dumazet 
Cc: Pavel Emelyanov 
Signed-off-by: Andrey Vagin 
Signed-off-by: David S. Miller

tcp: remove Appropriate Byte Count support

2013-02-05T19:51:16+00:00

TCP Appropriate Byte Count was added by me, but later disabled.
There is no point in maintaining it since it is a potential source
of bugs and Linux already implements other better window protection
heuristics.

Signed-off-by: Stephen Hemminger 
Signed-off-by: David S. Miller

net: Add support for hardware-offloaded encapsulation

2012-12-09T05:20:28+00:00

This patch adds support in the kernel for offloading in the NIC Tx and Rx
checksumming for encapsulated packets (such as VXLAN and IP GRE).

For Tx encapsulation offload, the driver will need to set the right bits
in netdev->hw_enc_features. The protocol driver will have to set the
skb->encapsulation bit and populate the inner headers, so the NIC driver will
use those inner headers to calculate the csum in hardware.

For Rx encapsulation offload, the driver will need to set again the
skb->encapsulation flag and the skb->ip_csum to CHECKSUM_UNNECESSARY.
In that case the protocol driver should push the decapsulated packet up
to the stack, again with CHECKSUM_UNNECESSARY. In ether case, the protocol
driver should set the skb->encapsulation flag back to zero. Finally the
protocol driver should have NETIF_F_RXCSUM flag set in its features.

Signed-off-by: Joseph Gasparakis 
Signed-off-by: Peter P Waskiewicz Jr 
Signed-off-by: Alexander Duyck 
Signed-off-by: David S. Miller

tcp: add SYN/data info to TCP_INFO

2012-10-22T19:16:06+00:00

Add a bit TCPI_OPT_SYN_DATA (32) to the socket option TCP_INFO:tcpi_options.
It's set if the data in SYN (sent or received) is acked by SYN-ACK. Server or
client application can use this information to check Fast Open success rate.

Signed-off-by: Yuchung Cheng 
Acked-by: Neal Cardwell 
Acked-by: Eric Dumazet 
Signed-off-by: David S. Miller

UAPI: (Scripted) Disintegrate include/linux

2012-10-13T09:46:48+00:00

Signed-off-by: David Howells 
Acked-by: Arnd Bergmann 
Acked-by: Thomas Gleixner 
Acked-by: Michael Kerrisk 
Acked-by: Paul E. McKenney 
Acked-by: Dave Jones

ipv4: Don't add TCP-code in inet_sock_destruct

2012-09-20T21:12:27+00:00

Signed-off-by: Christoph Paasch 
Acked-by: H.K. Jerry Chu 
Acked-by: Eric Dumazet 
Signed-off-by: David S. Miller

tcp: TCP Fast Open Server - header & support functions

2012-09-01T00:02:18+00:00

This patch adds all the necessary data structure and support
functions to implement TFO server side. It also documents a number
of flags for the sysctl_tcp_fastopen knob, and adds a few Linux
extension MIBs.

In addition, it includes the following:

1. a new TCP_FASTOPEN socket option an application must call to
supply a max backlog allowed in order to enable TFO on its listener.

2. A number of key data structures:
"fastopen_rsk" in tcp_sock - for a big socket to access its
request_sock for retransmission and ack processing purpose. It is
non-NULL iff 3WHS not completed.

"fastopenq" in request_sock_queue - points to a per Fast Open
listener data structure "fastopen_queue" to keep track of qlen (# of
outstanding Fast Open requests) and max_qlen, among other things.

"listener" in tcp_request_sock - to point to the original listener
for book-keeping purpose, i.e., to maintain qlen against max_qlen
as part of defense against IP spoofing attack.

3. various data structure and functions, many in tcp_fastopen.c, to
support server side Fast Open cookie operations, including
/proc/sys/net/ipv4/tcp_fastopen_key to allow manual rekeying.

Signed-off-by: H.K. Jerry Chu 
Cc: Yuchung Cheng 
Cc: Neal Cardwell 
Cc: Eric Dumazet 
Cc: Tom Herbert 
Signed-off-by: David S. Miller

tcp: dont drop MTU reduction indications

2012-07-23T07:58:46+00:00

ICMP messages generated in output path if frame length is bigger than
mtu are actually lost because socket is owned by user (doing the xmit)

One example is the ipgre_tunnel_xmit() calling
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));

We had a similar case fixed in commit a34a101e1e6 (ipv6: disable GSO on
sockets hitting dst_allfrag).

Problem of such fix is that it relied on retransmit timers, so short tcp
sessions paid a too big latency increase price.

This patch uses the tcp_release_cb() infrastructure so that MTU
reduction messages (ICMP messages) are not lost, and no extra delay
is added in TCP transmits.

Reported-by: Maciej Żenczykowski 
Diagnosed-by: Neal Cardwell 
Signed-off-by: Eric Dumazet 
Cc: Nandita Dukkipati 
Cc: Tom Herbert 
Cc: Tore Anderson 
Signed-off-by: David S. Miller

tcp: improve latencies of timer triggered events

2012-07-20T17:59:41+00:00

Modern TCP stack highly depends on tcp_write_timer() having a small
latency, but current implementation doesn't exactly meet the
expectations.

When a timer fires but finds the socket is owned by the user, it rearms
itself for an additional delay hoping next run will be more
successful.

tcp_write_timer() for example uses a 50ms delay for next try, and it
defeats many attempts to get predictable TCP behavior in term of
latencies.

Use the recently introduced tcp_release_cb(), so that the user owning
the socket will call various handlers right before socket release.

This will permit us to post a followup patch to address the
tcp_tso_should_defer() syndrome (some deferred packets have to wait
RTO timer to be transmitted, while cwnd should allow us to send them
sooner)

Signed-off-by: Eric Dumazet 
Cc: Tom Herbert 
Cc: Yuchung Cheng 
Cc: Neal Cardwell 
Cc: Nandita Dukkipati 
Cc: H.K. Jerry Chu 
Cc: John Heffner 
Signed-off-by: David S. Miller

net-tcp: Fast Open client - cookie-less mode

2012-07-19T18:02:03+00:00

In trusted networks, e.g., intranet, data-center, the client does not
need to use Fast Open cookie to mitigate DoS attacks. In cookie-less
mode, sendmsg() with MSG_FASTOPEN flag will send SYN-data regardless
of cookie availability.

Signed-off-by: Yuchung Cheng 
Acked-by: Eric Dumazet 
Signed-off-by: David S. Miller