p2ptbl: add gossip protocol

- add `p2ptbl gossip` to distribute tables via udp bcast
- add interface option to `p2ptbl update` for immediate communication
  of updates
- add p2ptbl-recv as HBBP-handler to receive table updates

p2ptbl-recv has to be symlinked from <HBBP-root>/p2ptbl/<table-name>.
It reads the table name from $0 and assumes that all tables are stored
in /tmp/p2ptbl/.

2 files changed, 73 insertions, 18 deletions

diff --git a/files/common/sbin/p2ptbl b/files/common/sbin/p2ptbl
index 8365915..a728a9c 100755
--- a/files/common/sbin/p2ptbl
+++ b/files/common/sbin/p2ptbl
@@ -1,25 +1,34 @@
 #!/bin/sh
 
-function init {
+set -e
+
+init () {
     [ -n "$1" ] || printArgs
-    [ -f "$1" ] || cat >$1 </dev/null
+    mkdir -p "$(dirname $1)"
+    [ -f "$1" ] || cat >"$1" </dev/null
 }
 
-function get {
+get () {
     [ -n "$2" ] || printArgs
-    grep -P "^$2\t" "$1" | cut -f3-
+    grep "^$2"$'\t' "$1" | cut -f3-
 }
 
-function update {
+update () {
     [ -n "$2" -a -n "$3" ] || printArgs
-    oldversion=$(grep -P "^$2\t" "$1" | cut -f2)
+    oldversion=$(grep "^$2"$'\t' "$1" | cut -f2)
     tmpfile="$1.update"
     echo -e "$2\t$(($oldversion + 1 + $RANDOM))\t$3" > "$tmpfile"
     merge "$1" "$tmpfile"
+    if [ -n "$4" ]; then
+	# broadcast update
+	gzip <"$tmpfile" >"$tmpfile.gz"
+	broadcaster $4 p2ptbl/$(basename "$1") - <"$tmpfile.gz"
+	rm "$tmpfile.gz"
+    fi
     rm "$tmpfile"
 }
 
-function merge {
+merge () {
     sort "$1" "$2" \
 	| {
 	oldkey=""
@@ -43,16 +52,41 @@ function merge {
     mv "$1~" "$1"
 }
 
-function printArgs {
+gossip() {
+    tgts="$2"
+    if="$3"
+    [ "$tgts" -gt 0 -a -n "$if" ] 2>/dev/null || printArgs
+
+    # binary search over number of sent lines until size is maximized
+    # and below target size
+    lc=$(wc -l <"$1")
+    [ $lc == 0 ] && return
+    shuf -v seed=$RANDOM <"$1" >"$1.gossip"
+    while [ $lc -ge 1 ]; do
+	head -n$lc "$1.gossip" | gzip >"$1.gossip.gz"
+	if [ $tgts -ge $(wc -c <"$1.gossip.gz") ]; then
+	    broadcaster $if p2ptbl/$(basename "$1") - <"$1.gossip.gz"
+	    rm "$1.gossip" "$1.gossip.gz"
+	    return;
+	fi
+	lc=$(($lc / 2))
+    done
+    rm "$1.gossip" "$1.gossip.gz"
+    echo "$1 has rows bigger then requested packet size"
+    exit 1
+}
+
+printArgs () {
     echo -e "Usage:
 $0 init   table
 $0 get    table key
-$0 update table key value
-$0 merge  table foreign-table"
-    exit -1
+$0 update table key value [interface]
+$0 merge  table foreign-table
+$0 gossip table target-size interface"
+    exit 1
 }
 
-function checkTable {
+checkTable () {
     [ -n "$1" ] || printArgs;
     [ -f "$1" ] || { 
 	echo "$1 is no P2P table"; 
@@ -60,24 +94,33 @@ function checkTable {
     }
 }
 
+lockTable () {
+    checkTable "$2"
+    exec 666<"$2"
+    flock "$1" 666
+}
+
 case "$1" in
     init) 
-	checkTable "$2"
 	init "$2"
 	;;
     get)
-	checkTable "$2"
+	lockTable -s "$2"
 	get "$2" "$3"
 	;;
     update)
-	checkTable "$2"
-	update "$2" "$3" "$4"
+	lockTable -s "$2"
+	update "$2" "$3" "$4" "$5"
 	;;
     merge)
-	checkTable "$2"
-	checkTable "$3"
+	lockTable -x "$2"
+	checkTable "$3" 
 	merge "$2" "$3"
 	;;
+    gossip)
+	lockTable -s "$2"
+	gossip "$2" "$3" "$4"
+	;;
     *) 
 	printArgs
 	;;
diff --git a/files/common/sbin/p2ptbl-recv b/files/common/sbin/p2ptbl-recv
new file mode 100755
index 0000000..f10fa39
--- /dev/null
+++ b/files/common/sbin/p2ptbl-recv
@@ -0,0 +1,12 @@
+#!/bin/sh
+
+set -e
+
+tbldir=/tmp/p2ptbl
+tbl=$tbldir/$(basename $0)
+
+[ -f $tbl ] || p2ptbl init $tbl
+
+gunzip > $tbl.recv
+p2ptbl merge $tbl $tbl.recv
+rm $tbl.recv
\ No newline at end of file