utils: add 'scan' feature to ixll

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

utils/ixll

@@ -22,6 +22,12 @@ may be supplied in places where a hostname is otherwise expected.
 
   Commands:
 
+    scan [-a] [<iface>]
+      Discover Infix devices on the LAN using mDNS-SD (avahi-browse).
+      Use -a to show all mDNS devices, not just Infix.  Falls back to
+      IPv6 link-local multicast ping if avahi-browse is not installed
+      and <iface> is specified.
+
     peer <iface>
       Return the address of the first IPv6 neighbor to respond on
       <iface>'s local LAN.
@@ -75,6 +81,9 @@ case "$cmd" in
     help)
 	usage && exit 0
 	;;
+    scan)
+	llscan "$@"
+	;;
     peer)
 	llpeer "$@"
 	;;

utils/libll.sh

@@ -144,3 +144,155 @@ llscp()
 
     $sshpasscmd scp $LLSCP_OPTS "$src" "$dst"
 }
+
+# Usage: llscan [-a] [<iface>]
+#
+# Discover Infix devices (or all mDNS devices with -a) on the LAN.
+# Prefers mDNS-SD via avahi-browse; falls back to IPv6 link-local
+# multicast ping if avahi-browse is not available and an interface
+# is specified.
+llscan()
+{
+    local all=0
+    local iface=
+
+    while [ $# -gt 0 ]; do
+	case "$1" in
+	    -a)
+		all=1
+		shift
+		;;
+	    *)
+		iface="$1"
+		shift
+		;;
+	esac
+    done
+
+    if [ "$iface" ] && [ ! -d "/sys/class/net/$iface" ]; then
+	echo "Error: Interface \"$iface\" does not exist." >&2
+	return 1
+    fi
+
+    if command -v avahi-browse >/dev/null 2>&1; then
+	llscan_mdns "$all"
+    elif [ "$iface" ]; then
+	echo "Note: avahi-browse not found, falling back to link-local scan." >&2
+	llscan_ll "$iface"
+    else
+	cat >&2 <<-EOF
+	Error: avahi-browse not found.
+
+	Install avahi-utils to scan for Infix devices via mDNS:
+	  sudo apt install avahi-utils
+
+	Or specify an interface to use IPv6 link-local fallback:
+	  $(basename $0) scan <iface>
+	EOF
+	return 1
+    fi
+}
+
+llscan_mdns()
+{
+    local all="$1"
+    local flags="-tarp"
+
+    if avahi-browse --help 2>&1 | grep -q -- '-k'; then
+	flags="-tarpk"
+    fi
+
+    avahi-browse $flags | awk -F';' -v show_all="$all" '
+    $1 == "=" {
+	host = $7
+	proto = $3
+	addr = $8
+	txt  = $10
+
+	on = ""; ov = ""; product = ""; serial = ""; devid = ""
+	n = split(txt, parts, "\" \"")
+	for (i = 1; i <= n; i++) {
+	    gsub(/"/, "", parts[i])
+	    if      (parts[i] ~ /^on=/)       { split(parts[i], kv, "="); on      = kv[2] }
+	    else if (parts[i] ~ /^ov=/)       { split(parts[i], kv, "="); ov      = kv[2] }
+	    else if (parts[i] ~ /^product=/)  { split(parts[i], kv, "="); product = kv[2] }
+	    else if (parts[i] ~ /^serial=/)   { split(parts[i], kv, "="); serial  = kv[2] }
+	    else if (parts[i] ~ /^deviceid=/) { split(parts[i], kv, "="); devid   = kv[2] }
+	}
+
+	if (!show_all && on != "Infix") next
+
+	# Use deviceid (MAC) as unique key; fall back to hostname
+	key = devid ? devid : host
+
+	if (!product) product = on ? on : "-"
+	if (!ov)      ov      = "-"
+	if (!serial || serial == "null") serial = "-"
+
+	# Prefer IPv4 for display address
+	if (proto == "IPv4") {
+	    ipv4[key] = addr
+	} else if (proto == "IPv6" && !ipv6[key]) {
+	    ipv6[key] = addr
+	}
+
+	if (!seen[key]++) {
+	    keys[++ndevs]  = key
+	    hosts[key]     = host
+	    products[key]  = product
+	    versions[key]  = ov
+	    serials[key]   = serial
+	} else if (length(host) > length(hosts[key])) {
+	    # Prefer the unique hostname (e.g., infix-c0-ff-ee.local)
+	    # over the generic one (e.g., infix.local)
+	    hosts[key] = host
+	}
+    }
+
+    END {
+	if (ndevs == 0) {
+	    if (show_all)
+		print "No mDNS devices found." | "cat >&2"
+	    else
+		print "No Infix devices found. Use -a to show all mDNS devices." | "cat >&2"
+	    exit 1
+	}
+
+	fmt = "%-26s %-18s %-24s %-22s %s\n"
+	hdr = sprintf(fmt, "HOSTNAME", "ADDRESS", "PRODUCT", "VERSION", "SERIAL")
+	sub(/\n$/, "", hdr)
+	printf "\033[7m%s\033[0m\n", hdr
+
+	for (i = 1; i <= ndevs; i++) {
+	    k = keys[i]
+	    a = (ipv4[k] ? ipv4[k] : (ipv6[k] ? ipv6[k] : "-"))
+	    p = products[k]; if (length(p) > 23) p = substr(p, 1, 22) "~"
+	    v = versions[k]; if (length(v) > 21) v = substr(v, 1, 20) "~"
+	    printf fmt, hosts[k], a, p, v, serials[k]
+	}
+
+	printf "\n%d device(s) found.\n", ndevs
+    }
+    '
+}
+
+llscan_ll()
+{
+    local iface="$1"
+
+    printf "Scanning %s for IPv6 link-local neighbors ...\n\n" "$iface"
+    printf "\033[7m%-6s %s\033[0m\n" "#" "ADDRESS"
+
+    llping "$iface" -c3 -w3 2>/dev/null | awk '
+    /bytes from/ {
+	sub(/:$/, "", $4)
+	addr = $4
+	if (!seen[addr]++) {
+	    printf "%-6d %s\n", ++n, addr
+	}
+    }
+    END {
+	printf "\n%d neighbor(s) found on '"$iface"'.\n", n+0
+    }
+    '
+}