feat: Add an example for icmp6

Signed-off-by: Jianhui Zhao <zhaojh329@gmail.com>

examples/network/ping6.lua

@@ -0,0 +1,96 @@
+#!/usr/bin/env eco
+
+--[[
+    to allow root to use icmp6 sockets, run:
+    sysctl -w net.ipv4.ping_group_range="0 0"
+--]]
+
+local socket = require 'eco.socket'
+local time = require 'eco.time'
+
+local ICMP6_HEADER_LEN = 8
+local ICMP6_ECHO = 128
+local ICMP6_ECHOREPLY = 129
+
+local dest_ip = '::1'
+local local_id = math.random(0, 65535)
+local local_seq = 1
+local local_data = 'hello'
+
+local function build_icmp_req()
+    local data = {
+        string.char(ICMP6_ECHO), -- type
+        '\0',        -- code
+        '\0\0',      -- checksum
+        '\0\0',      -- id: the kernel will assign it with local port
+        string.char(local_seq >> 8, local_seq & 0xff),   -- sequence
+        local_data
+    }
+
+    local_seq = local_seq + 1
+
+    return table.concat(data)
+end
+
+local function parse_icmp_resp(data)
+    if #data < ICMP6_HEADER_LEN then
+        return nil, 'invalid icmp resp'
+    end
+
+    local icmp_type = data:byte(1)
+    local id_hi = data:byte(5)
+    local id_lo = data:byte(6)
+    local id = (id_hi << 8) + id_lo
+
+    local seq_hi = data:byte(7)
+    local seq_lo = data:byte(8)
+    local seq = (seq_hi << 8) + seq_lo
+
+    return icmp_type, id, seq, #data - ICMP6_HEADER_LEN
+end
+
+local s, err = socket.icmp6()
+if not s then
+    print(err)
+    return
+end
+
+-- s:setoption('bindtodevice', 'eth0')
+
+s:bind(nil, local_id)
+
+print(string.format('PING %s, %d bytes of data.', dest_ip, #local_data))
+
+while true do
+    _, err = s:sendto(build_icmp_req(), dest_ip, 0)
+    if err then
+        print('send fail:', err)
+        break
+    end
+
+    local start = time.now()
+
+    local resp, peer = s:recvfrom(1024, 5.0)
+    if not resp then
+        print('recv fail:', peer)
+        break
+    end
+
+    local elapsed = time.now() - start
+
+    local icmp_type, id, seq, n = parse_icmp_resp(resp)
+
+    if icmp_type then
+        if icmp_type == ICMP6_ECHOREPLY then
+            if id == local_id then
+                print(string.format('%d bytes from %s: icmp_seq=%d time=%.3f ms', n, dest_ip, seq, elapsed * 1000))
+            end
+        else
+            print('Got ICMP packet with type ' .. icmp_type)
+        end
+    else
+        print(id)
+    end
+
+    time.sleep(1.0)
+end