Add port FEC BER feature swss, HLD#1829 (sonic-net#3363)

What I did
This is to add the swss changes for the feature port FEC BER.
It modify the port_rates.lua script to compute the BER and stored them in the DB .
Two additonal PR(s) will address the cli ( sonic-utilities) and the sonic-mgmt changes

Why I did it
The HLD for this feature is HLD#1829

How I verified it
We verify the counters internally
(1) verify when link has correctable FEC errors, the BER were calcuated accordingly
(2) verify 400G with 4x100 and the BER , four serdes with 100G rate
(3) run a redis-script to polling the DB counters and verify the calculation
(4) stop polling manually modify the uncorrectable counter and verify the cli display and calculation

Author: vincentpcng

orchagent/port_rates.lua

@@ -13,6 +13,9 @@ end
 local counters_db = ARGV[1]
 local counters_table_name = ARGV[2]
 local rates_table_name = "RATES"
+local appl_db_port = "PORT_TABLE"
+--  refer back to common/schema.h
+local appl_db = "0"
 
 -- Get configuration
 redis.call('SELECT', counters_db)
@@ -29,11 +32,117 @@ logit(alpha)
 logit(one_minus_alpha)
 logit(delta)
 
+local port_interface_oid_map = redis.call('HGETALL', "COUNTERS_PORT_NAME_MAP")
+local port_interface_oid_key_count = redis.call('HLEN', "COUNTERS_PORT_NAME_MAP")
+
+-- lookup interface name from port oid
+
+local function find_interface_name_from_oid(port)
+
+    for i = 1, port_interface_oid_key_count do
+        local index = i * 2 - 1
+        if port_interface_oid_map[index + 1] == port then
+            return port_interface_oid_map[index]
+        end
+    end
+
+    return 0
+end
+
+-- calculate lanes and serdes speed from interface lane count & speed
+-- return lane speed and serdes speed
+
+local function calculate_lane_and_serdes_speed(count, speed)
+
+   local serdes = 0
+   local lane_speed = 0
+
+    if count == 0 or speed == 0 then
+        logit("Invalid number of lanes or speed")
+        return 0, 0
+    end
+
+    -- check serdes_cnt if it is a multiple of speed
+    local serdes_cnt = math.fmod(speed, count)
+
+    if serdes_cnt ~= 0 then
+        logit("Invalid speed and number of lanes combination")
+        return 0, 0
+    end
+
+    lane_speed = math.floor(speed / count)
+
+    -- return value in bits
+    if lane_speed == 1000 then
+        serdes = 1.25e+9
+    elseif lane_speed == 10000 then
+        serdes = 10.3125e+9
+    elseif lane_speed == 25000 then
+        serdes = 25.78125e+9
+    elseif lane_speed == 50000 then
+        serdes = 53.125e+9
+    elseif lane_speed == 100000 then
+        serdes = 106.25e+9
+    else
+       logit("Invalid serdes speed")
+    end
+
+    return lane_speed, serdes
+end
+
+-- look up interface lanes count, lanes speed & serdes speed
+-- return lane count, lane speed, serdes speed
+
+local function find_lanes_and_serdes(interface_name)
+    -- get the port config from config db
+    local _
+    local serdes, lane_speed, count = 0, 0, 0
+
+    -- Get the port configure
+    redis.call('SELECT', appl_db)
+    local lanes = redis.call('HGET', appl_db_port ..':'..interface_name, 'lanes')
+
+    if lanes then
+        local speed = redis.call('HGET', appl_db_port ..':'..interface_name, 'speed')
+
+        -- we were spliting it on ','
+        _, count = string.gsub(lanes, ",", ",")
+        count = count + 1
+
+        lane_speed, serdes = calculate_lane_and_serdes_speed(count, speed)
+
+    end
+    -- switch back to counter db
+    redis.call('SELECT', counters_db)
+
+    return count, lane_speed, serdes
+end
+
 local function compute_rate(port)
+
     local state_table = rates_table_name .. ':' .. port .. ':' .. 'PORT'
     local initialized = redis.call('HGET', state_table, 'INIT_DONE')
     logit(initialized)
 
+    -- FEC BER
+    local fec_corr_bits, fec_uncorr_frames
+    local fec_corr_bits_ber_new, fec_uncorr_bits_ber_new = -1, -1
+    -- HLD review suggest to use the statistical average when calculate the post fec ber
+    local rs_average_frame_ber = 1e-8
+    local lanes_speed, serdes_speed, lanes_count = 0, 0, 0
+
+    -- lookup interface name from oid
+    local interface_name = find_interface_name_from_oid(port)
+    if interface_name then
+        lanes_count, lanes_speed, serdes_speed = find_lanes_and_serdes(interface_name)
+ 
+        if lanes_count and serdes_speed then
+            fec_corr_bits = redis.call('HGET', counters_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_IN_FEC_CORRECTED_BITS')
+            fec_uncorr_frames = redis.call('HGET', counters_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_IN_FEC_NOT_CORRECTABLE_FRAMES')
+        end
+    end
+
+
     -- Get new COUNTERS values
     local in_ucast_pkts = redis.call('HGET', counters_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_IN_UCAST_PKTS')
     local in_non_ucast_pkts = redis.call('HGET', counters_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_IN_NON_UCAST_PKTS')
@@ -58,10 +167,11 @@ local function compute_rate(port)
         local out_octets_last = redis.call('HGET', rates_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_OUT_OCTETS_last')
 
         -- Calculate new rates values
-        local rx_bps_new = (in_octets - in_octets_last) / delta * 1000
-        local tx_bps_new = (out_octets - out_octets_last) / delta * 1000
-        local rx_pps_new = ((in_ucast_pkts + in_non_ucast_pkts) - (in_ucast_pkts_last + in_non_ucast_pkts_last)) / delta * 1000
-        local tx_pps_new = ((out_ucast_pkts + out_non_ucast_pkts) - (out_ucast_pkts_last + out_non_ucast_pkts_last)) / delta * 1000
+        local scale_factor = 1000 / delta
+        local rx_bps_new = (in_octets - in_octets_last) * scale_factor 
+        local tx_bps_new = (out_octets - out_octets_last) * scale_factor
+        local rx_pps_new = ((in_ucast_pkts + in_non_ucast_pkts) - (in_ucast_pkts_last + in_non_ucast_pkts_last)) * scale_factor
+        local tx_pps_new = ((out_ucast_pkts + out_non_ucast_pkts) - (out_ucast_pkts_last + out_non_ucast_pkts_last)) * scale_factor
 
         if initialized == "DONE" then
             -- Get old rates values
@@ -83,6 +193,21 @@ local function compute_rate(port)
             redis.call('HSET', rates_table_name .. ':' .. port, 'TX_PPS', tx_pps_new)
             redis.call('HSET', state_table, 'INIT_DONE', 'DONE')
         end
+
+        -- only do the calculation when all info present
+        
+        if fec_corr_bits and fec_uncorr_frames and lanes_count and serdes_speed then
+            local fec_corr_bits_last = redis.call('HGET', rates_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_FEC_CORRECTED_BITS_last')
+            local fec_uncorr_frames_last = redis.call('HGET', rates_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_FEC_NOT_CORRECTABLE_FARMES_last')
+
+            local serdes_rate_total = lanes_count * serdes_speed * delta / 1000
+
+            fec_corr_bits_ber_new = (fec_corr_bits - fec_corr_bits_last) / serdes_rate_total
+            fec_uncorr_bits_ber_new = (fec_uncorr_frames - fec_uncorr_frames_last) * rs_average_frame_ber  / serdes_rate_total
+        else
+            logit("FEC counters or lane info not found on " .. port)
+        end
+
     else
         redis.call('HSET', state_table, 'INIT_DONE', 'COUNTERS_LAST')
     end
@@ -94,6 +219,19 @@ local function compute_rate(port)
     redis.call('HSET', rates_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_OUT_NON_UCAST_PKTS_last', out_non_ucast_pkts)
     redis.call('HSET', rates_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_IN_OCTETS_last', in_octets)
     redis.call('HSET', rates_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_OUT_OCTETS_last', out_octets)
+
+    -- do not update FEC related stat if we dont have it
+    
+    if not fec_corr_bits or not fec_uncorr_frames or not fec_corr_bits_ber_new or
+       not fec_uncorr_bits_ber_new then
+        logit("FEC counters not found on " .. port)
+        return
+    end
+    -- Set BER values
+    redis.call('HSET', rates_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_FEC_CORRECTED_BITS_last', fec_corr_bits)
+    redis.call('HSET', rates_table_name .. ':' .. port, 'SAI_PORT_STAT_IF_FEC_NOT_CORRECTABLE_FARMES_last', fec_uncorr_frames)
+    redis.call('HSET', rates_table_name .. ':' .. port, 'FEC_PRE_BER', fec_corr_bits_ber_new)
+    redis.call('HSET', rates_table_name .. ':' .. port, 'FEC_POST_BER', fec_uncorr_bits_ber_new)
 end
 
 local n = table.getn(KEYS)