[FIB] Updated packets to send per next hop group when check balancing

[SavchukRomanLv]

Signed-off-by: Roman Savchuk [email protected]

Description of PR

Summary:
When run fib case on t0 topology we receive check_balancing error. After investigation was found, that BGP sessions flaps because PTF generates too many packets to test each IP range. This affects TCP sessions on VMs side. For t0 topology we have 4 next hop groups(Port Channels). For t1 topology number for next_hop groups is 16.

Type of change

• [+ ] Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Approach

What is the motivation for this PR?

Make fib TC passed on t0

How did you do it?

Test case itself sends every time 10000 packets for all topos.
To include specialty of each topo I decided to use weighting factors based on topo type, as an ethalon I've taken load per group in t1 topo. New BALANCING_TEST_TIMES = 625 (10000/16). Based of number of next_hop group in topo this BALANCING_TEST_TIMES will be multiply on this number for checking balancing.

Also small delays (0.01 sec) was being added when send balancing traffic not to overload TCP sessions.

How did you verify/test it?

Run fib TC on t0 topo

Any platform specific information?

SONiC Software Version: SONiC.master.35-dirty-20201112.031542
Distribution: Debian 10.6
Kernel: 4.19.0-9-2-amd64
Build commit: 6c362a0
Build date: Thu Nov 12 11:49:55 UTC 2020
Platform: x86_64-accton_wedge100bf_32x-r0
HwSKU: montara
ASIC: barefoot

Supported testbed topology if it's a new test case?

Documentation

[SavchukRomanLv]

Pls review @wangxin @yxieca

[wangxin]

Why need this delay?

If this delay is really needed, should it be added to the loop in function def check_ip_ranges?

    def check_ip_ranges(self, ipv4=True):
        if ipv4:
            ip_ranges = self.fib.ipv4_ranges()
        else:
            ip_ranges = self.fib.ipv6_ranges()

        for ip_range in ip_ranges:
            if ip_range.get_first_ip() in self.fib:
                next_hop = self.fib[ip_range.get_first_ip()]
                self.check_ip_range(ip_range, next_hop, ipv4)
                time.sleep(0.01)

[SavchukRomanLv]

Yes, we need this tiny sleep to avoid flapping bgp sessions, as TC received ~6k routes per neighbor, and sends 3 packets per route group. To avoid overloading when send traffic delay was being set.

In def check_ip_ranges i beleive we do not need such delay, I've re-run fib dozen times and TC passed without changes in check_ip_ranges.