src/connectivity/network/netstack/README.md

# Netstack

Netstack is a userspace TCP/IP network stack and interfaces with zircon
network drivers.
Netstack serves as a back-end for fdio socket API.

     +-----------+           +-----------+
     | FIDL app  |           | POSIX app |
     +--+--------+           +-----+-----+
        |                          |
        |                          |
        |                          |
        |                          |
        |                          |
        |                          |
        |   +----------------------v---------+
        |   |         BSD socket API         |
        |   |  (//sdk/lib/fdio)   |
        |   +---------+----------------------+
        |             |
     +--v-------------v----------------------+
     |            netstack                   |
     | (//src/connectivity/network/netstack) |
     +----------------+----------------------+
                      |
     +----------------v-----------------+
     |         Ethernet driver          |
     | (//zircon/system/udev/ethernet)  |
     +----------------------------------+

## Benchmarking

netstack microbenchmarks are in package netstack/bench; they can be run via the target netstack_bench_test.

To run the benchmarks and obtain profiling data:

    REALM=bench
    PROFILE_PATH=/data/r/sys/r/$REALM/fuchsia.com:netstack_gotests:0#meta:netstack_bench_test.cmx/profile
    fx build netstack_gotests \
      && fx test -o -R=$REALM netstack_bench_test \
      && fx scp "[$(fx get-device-addr)]:$PROFILE_PATH" out/profile \
      && go tool pprof -http=:8080 out/profile

Example output (astro):

    goos: fuchsia
    goarch: arm64
    pkg: netstack/bench
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=2048-4                  190443              6513 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=1024-4                  247176              4831 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=512-4                   326691              3842 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=256-4                   364168              3426 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=128-4                   394536              3282 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=64-4                    405102              3218 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=32-4                    423908              2967 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=16-4                    424617              2931 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=8-4                     386036              2935 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=4-4                     404241              2990 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=2-4                     371358              2887 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadDisabled/len(payload)=1-4                     431478              2889 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=2048-4                   461614              2766 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=1024-4                   417296              2924 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=512-4                    474790              2814 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=256-4                    453231              2832 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=128-4                    472670              2835 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=64-4                     469988              2894 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=32-4                     490627              2614 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=16-4                     485992              2753 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=8-4                      492573              2798 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=4-4                      487836              2923 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=2-4                      434959              2658 ns/op             112 B/op          3 allocs/op
    BenchmarkWritePacket/checksumOffloadEnabled/len(payload)=1-4                      490470              3010 ns/op             112 B/op          3 allocs/op