sflow

SFlow Input Plugin

The SFlow Input Plugin provides support for acting as an SFlow V5 collector in accordance with the specification from sflow.org.

Currently only Flow Samples of Ethernet / IPv4 & IPv4 TCP & UDP headers are turned into metrics. Counters and other header samples are ignored.

Series Cardinality Warning

This plugin may produce a high number of series which, when not controlled for, will cause high load on your database. Use the following techniques to avoid cardinality issues:

• Use metric filtering options to exclude unneeded measurements and tags.
• Write to a database with an appropriate retention policy.
• Limit series cardinality in your database using the max-series-per-database and max-values-per-tag settings.
• Consider using the Time Series Index.
• Monitor your databases series cardinality.
• Consult the InfluxDB documentation for the most up-to-date techniques.

Configuration

[[inputs.sflow]]
  ## Address to listen for sFlow packets.
  ##   example: service_address = "udp://:6343"
  ##            service_address = "udp4://:6343"
  ##            service_address = "udp6://:6343"
  service_address = "udp://:6343"

  ## Set the size of the operating system's receive buffer.
  ##   example: read_buffer_size = "64KiB"
  # read_buffer_size = ""

Metrics

• sflow
  • tags:
    • agent_address (IP address of the agent that obtained the sflow sample and sent it to this collector)
    • source_id_type(source_id_type field of flow_sample or flow_sample_expanded structures)
    • source_id_index(source_id_index field of flow_sample or flow_sample_expanded structures)
    • input_ifindex (value (input) field of flow_sample or flow_sample_expanded structures)
    • output_ifindex (value (output) field of flow_sample or flow_sample_expanded structures)
    • sample_direction (source_id_index, netif_index_in and netif_index_out)
    • header_protocol (header_protocol field of sampled_header structures)
    • ether_type (eth_type field of an ETHERNET-ISO88023 header)
    • src_ip (source_ipaddr field of IPv4 or IPv6 structures)
    • src_port (src_port field of TCP or UDP structures)
    • src_port_name (src_port)
    • src_mac (source_mac_addr field of an ETHERNET-ISO88023 header)
    • src_vlan (src_vlan field of extended_switch structure)
    • src_priority (src_priority field of extended_switch structure)
    • src_mask_len (src_mask_len field of extended_router structure)
    • dst_ip (destination_ipaddr field of IPv4 or IPv6 structures)
    • dst_port (dst_port field of TCP or UDP structures)
    • dst_port_name (dst_port)
    • dst_mac (destination_mac_addr field of an ETHERNET-ISO88023 header)
    • dst_vlan (dst_vlan field of extended_switch structure)
    • dst_priority (dst_priority field of extended_switch structure)
    • dst_mask_len (dst_mask_len field of extended_router structure)
    • next_hop (next_hop field of extended_router structure)
    • ip_version (ip_ver field of IPv4 or IPv6 structures)
    • ip_protocol (ip_protocol field of IPv4 or IPv6 structures)
    • ip_dscp (ip_dscp field of IPv4 or IPv6 structures)
    • ip_ecn (ecn field of IPv4 or IPv6 structures)
    • tcp_urgent_pointer (urgent_pointer field of TCP structure)
  • fields:
    • bytes (integer, the product of frame_length and packets)
    • drops (integer, drops field of flow_sample or flow_sample_expanded structures)
    • packets (integer, sampling_rate field of flow_sample or flow_sample_expanded structures)
    • frame_length (integer, frame_length field of sampled_header structures)
    • header_size (integer, header_size field of sampled_header structures)
    • ip_fragment_offset (integer, ip_ver field of IPv4 structures)
    • ip_header_length (integer, ip_ver field of IPv4 structures)
    • ip_total_length (integer, ip_total_len field of IPv4 structures)
    • ip_ttl (integer, ip_ttl field of IPv4 structures or ip_hop_limit field IPv6 structures)
    • tcp_header_length (integer, size field of TCP structure. This value is specified in 32-bit words. It must be multiplied by 4 to produce a value in bytes.)
    • tcp_window_size (integer, window_size field of TCP structure)
    • udp_length (integer, length field of UDP structures)
    • ip_flags (integer, ip_ver field of IPv4 structures)
    • tcp_flags (integer, TCP flags of TCP IP header (IPv4 or IPv6))

Troubleshooting

The sflowtool utility can be used to print sFlow packets, and compared against the metrics produced by Telegraf.

sflowtool -p 6343

If opening an issue, in addition to the output of sflowtool it will also be helpful to collect a packet capture. Adjust the interface, host and port as needed:

$ sudo tcpdump -s 0 -i eth0 -w telegraf-sflow.pcap host 127.0.0.1 and port 6343

Example Output

sflow,agent_address=0.0.0.0,dst_ip=10.0.0.2,dst_mac=ff:ff:ff:ff:ff:ff,dst_port=40042,ether_type=IPv4,header_protocol=ETHERNET-ISO88023,input_ifindex=6,ip_dscp=27,ip_ecn=0,output_ifindex=1073741823,source_id_index=3,source_id_type=0,src_ip=10.0.0.1,src_mac=ff:ff:ff:ff:ff:ff,src_port=443 bytes=1570i,drops=0i,frame_length=157i,header_length=128i,ip_flags=2i,ip_fragment_offset=0i,ip_total_length=139i,ip_ttl=42i,sampling_rate=10i,tcp_header_length=0i,tcp_urgent_pointer=0i,tcp_window_size=14i 1584473704793580447