Merge branch 'tcp_metrics_saddr'

Christoph Paasch says:

====================
Make tcp-metrics source-address aware

Currently tcp-metrics only stores per-destination addresses. This brings
problems, when a host has multiple interfaces (e.g., a smartphone having
WiFi/3G):

For example, a host contacting a server over WiFi will store the tcp-metrics
per destination IP. If then the host contacts the same server over 3G, the
same tcp-metrics will be used, although the path-characteristics are completly
different (e.g., the ssthresh is probably not the same).

In case of TFO this is not a problem, as the server will provide us a new cookie
once he saw our SYN+DATA with an incorrect cookie.
It may be (in case of carrier-grade NAT), that we keep the same public IP but
have a different private IP. Thus, we better reuse the old cookie even if our
source-IP has changed. However, this scenario is probably very uncommon, as
carriers try to provide the same src-IP to the clients behind their CGN.

Patches 1 + 2 add the source-IP to the tcp metrics.

Patches 3 to 5 modify the netlink-api to support the source-IP. From now on,
when using the command "ip tcp_metrics delete address ADDRESS" all entries
which match this destination IP will be deleted.

Today's iproute2 will complain when doing "ip tcp_metrics flush PREFIX" if
several entries are present for the same destination-IP but with different
source-IPs:

root@client:~/test# ip tcp_metrics
10.2.1.2 age 3.640sec rtt 16250us rttvar 15000us cwnd 10
10.2.1.2 age 4.030sec rtt 18750us rttvar 15000us cwnd 10
root@client:~/test# ip tcp_metrics flush 10.2.1.2/16
Failed to send flush request
: No such process

Follow-up patches will modify iproute2 to handle this correctly and allow
specifying the source-IP in the get/del commands.

v2: Added the patch that allows to selectively get/del of tcp-metrics based
    on src-IP and moved the patch that adds the new netlink attribute before
    the other patches.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>