bgpd: use ATTR_FLAG_BIT() for BGP_ATTR_ values

* bgp_attr.c: this UNSET_FLAG()s are bogus. I did a quick review and
  I think that they could not cause any bug anyway.

Signed-off-by: Jorge Boncompte [DTI2] <jorge@dti2.net>
Acked-by: Feng Lu <lu.feng@6wind.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: add 'bgp bestpath as-path multipath-relax'

Compute multipath in BGP based on AS_PATH hop count match. If the knob
is turned on, it is not required to have an exact match of AS_PATHs
(provided other multipath conditions are met, of course).

Signed-off-by: Pradosh Mohapatra <pmohapat at cumulusnetworks.com>
Reviewed-by: Dinesh G Dutt <ddutt at cumulusnetworks.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: track correct originator-id in reflected routes

ISSUE:

Suppose route1 and route2 received from route-reflector-client1 and client2
respectively have identical attributes. The current logic of creating the
adj-rib-out for a peer threads the 'adv' structures for both routes against
the same attribute. This results in 'bgp_update_packet()' to pack those
routes in the same UPDATE message with one attr structure formatted. The
originator-id is thus set according to the first route's received router id.
This is incorrect.

PATCH:

Fix bgp_announce_check() function to set the originator-id in the
advertising attr structure. Also, fix the attribute hash function and
compare function to consider originator-id. Otherwise attributes where all
fields except the originator-id are identical get merged into one memory
location.

Signed-off-by: Pradosh Mohapatra <pmohapat at cumulusnetworks.com>
Reviewed-by: Scott Feldman <sfeldma at cumulusnetworks.com>
Reviewed-by: Ken Yin <kyin at cumulusnetworks.com>
[DL: whitespace changes dropped]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: display multipath status in "show ip bgp"

The output of "show ip bg" does not show whether and which routes are
installed as multipath routes along the best route:

BGP table version is 0, local router ID is 10.10.100.209
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*>i1.0.0.0/24       10.10.100.1              1    111      0 15169 i
* i                 10.10.100.2              1    111      0 15169 i
* i                 10.10.100.3              1    111      0 65100 15169 i

This patch adds a new status code that is showing exactly which routes
are used as multipath:

BGP table version is 0, local router ID is 10.10.100.209
Status codes: s suppressed, d damped, h history, * valid, > best, = multipath,
              i internal, r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*>i1.0.0.0/24       10.10.100.1              1    111      0 15169 i
*=i                 10.10.100.2              1    111      0 15169 i
* i                 10.10.100.3              1    111      0 65100 15169 i

The inconsistency in the status code legend ("i - internal" vs. "i internal")
inherent from old IOS was fixed. It had to be touched anyways.

Signed-off-by: Boian Bonev <bbonev at ipacct.com>
[DL: rewrap long line, clean whitespace in same chunk]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: send notify in OpenSent when stopping manually

The issue it fixes is that the notification message is not sent to a
second peer when bgp is stopped manually.

According to BGP RFC4271, section 8.2.2, regarding the FSM transitions,
in OpenSent state:

If a ManualStop event (Event 2) is issued in the OpenSent state, the
local system:

  * sends the NOTIFICATION with a Cease,
  * sets the ConnectRetryTimer to zero,
  * releases all BGP resources,
  * drops the TCP connection,
  * sets the ConnectRetryCounter to zero, and
  * changes its state to Idle.

I've added a check for OpenSent state when the notification is sent from
the functions which are called from the CLI commands which
directly/indirectly stop/restart BGP.

Acked-by: Pradosh Mohapatra <pmohapat@cumulusnetworks.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: fix O_NONBLOCK on outgoing connects

BGP was setting sockets to be non-blocking only for the accepted passive
peers.  As a fix, setting the BGP sockets to be non-blocking even for
the active peers.

Signed-off-by: Vipin Kumar <vipin@cumulusnetworks.com>
Reviewed-by: Pradosh Mohapatra <pmohapat@cumulusnetworks.com>
Reviewed-by: Dinesh Dutt <ddutt@cumulusnetworks.com>
[DL: patch split, this is item 1.]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: increase TCP socket buffer size

BGP does not respond fairly in high scale.  As the number of BGP peers
and prefixes increase, triggers like interface flaps which lead to BGP
peer flaps, cause blockage in bgp_write.

BGP does handle the cases of TCP socket buffer full by queuing a write
event back, there is no functional issue there as such. Still,
increasing the peer socket buffer size should help reduce event queueing
in BGP.

Signed-off-by: Vipin Kumar <vipin@cumulusnetworks.com>
Reviewed-by: Pradosh Mohapatra <pmohapat@cumulusnetworks.com>
Reviewed-by: Dinesh Dutt <ddutt@cumulusnetworks.com>
[DL: patch split, this is item 3.]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: fix fast external fallover behavior

ISSUES

1. When an interface goes down, the zclient callbacks are invoked
   in the following order: (a) address_delete() that removes the
   connected address list: ifp->connected, (b) interface_down()
   that performs "fast external fallover" operation. The operation
   relies on ifp->connected to look for peers that should be brought
   down. That's a cyclic dependency.

2. 'ttl-security' configuration handler sets peer->ttl to
   MAXTTL (so that BGP packets are sent with TTL=255, as per the
   requirement of ttl-security). This, however, is incompatible
   with 'fast external fallover' as the fallover operation checks
   for (ttl == 1) to determine directly connected peers.

3. The current fallover operation does not work for IPv6 address family.

PATCH

1. The patch removes the dependency on 'ifp->connected' list for fast
   fallover. The peer already contains a nexthop structure that reflects
   the peering address. The nexthop structure has a pointer to the
   interface (ifp) that peering address resolves to. Everytime the TCP
   connection succeeds, the ifp is updated. The patch uses this ifp in
   the interface_down() callback for a match for the peers that should be
   brought down.

2. The evaluation for directly connected peering is enhanced as
   'peer->ttl == 1' OR 'peer->gtsm_hops == 1'. Thus a ttl-security
   configuration on the peer with one hop is directly connected and
   should be brought down under 'fast external fallover'.

3. Because of fix (1), IPv6 address family works automatically.

Signed-off-by: Pradosh Mohapatra <pmohapat@cumulusnetworks.com>
Reviewed-by: Dinesh G Dutt <ddutt@cumulusnetworks.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: factor out TTL setting

TTL/min TTL are set from both bgp_accept() and bgp_connect().  Factor
them out so the following change to enable iBGP GTSM becomes more
readable.

[DL: originally by Dinesh G Dutt <ddutt@cumulusnetworks.com>,
     split off from the next commit]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: factor out eBGP multihop check

The check for an eBGP multihop configuration is unwieldy;  factor it out
into a separate function.

[DL: originally by Dinesh G Dutt <ddutt@cumulusnetworks.com>,
     split off from the next commit]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: support TTL-security with iBGP

Traditionally, ttl-security feature has been associated with EBGP
sessions as those identify directly connected external peers. The
GTSM RFC (rfc 5082) does not make any restrictions on type of
peering. In fact, it is beneficial to support ttl-security for both
EBGP and IBGP sessions. Specifically, in data centers, there are
directly connected IBGP peerings that will benefit from the protection
ttl-security provides.

Signed-off-by: Dinesh G Dutt <ddutt@cumulusnetworks.com>
Reviewed-by: Pradosh Mohapatra <pmohapat@cumulusnetworks.com>
[DL: function refactoring split out into previous 2 patches.  changes:
     - bgp_set_socket_ttl(): ret type int -> void
     - is_ebgp_multihop_configured(): stripped peer == NULL check
     - comments/whitespace]
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
bgpd: Fix condition allowas-in in rsclient code

Currently when you set neighbour's 'allowas-in' option on route server side
you get redistribution of the prefixes from this neighbour's table into all
neighbour's tables which have the same AS number. I think that wanted behaviour
is to allow import prefixes from neighbour's tables with the same AS num
into neighbour which has 'allowas-in' option set.

Signed-off-by: Milan Kocian <milon@wq.cz>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>