[linux] Display connection state for UDP sockets

Makefile.am

@@ -153,6 +153,7 @@ LINUX_TESTS = lib/dialects/linux/tests/case-10-mqueue.bash \
 	lib/dialects/linux/tests/case-20-inet6-socket-endpoint.bash \
 	lib/dialects/linux/tests/case-20-inet-socket-endpoint.bash \
 	lib/dialects/linux/tests/case-20-mmap.bash \
+	lib/dialects/linux/tests/case-20-udp-socket-state.bash \
 	lib/dialects/linux/tests/case-20-mqueue-endpoint.bash \
 	lib/dialects/linux/tests/case-20-open-flags-cx.bash \
 	lib/dialects/linux/tests/case-20-open-flags-path.bash \

lib/dialects/linux/dsock.c

@@ -401,6 +401,17 @@ void build_IPstates(struct lsof_context *ctx) {
         (void)enter_IPstate(ctx, "TCP", "CLOSED", 0);
         (void)enter_IPstate(ctx, "TCP", (char *)NULL, 0);
     }
+    if (!UdpSt) {
+        /*
+         * Linux /proc/net/udp reuses TCP state enum values:
+         * TCP_ESTABLISHED (1) for connected UDP sockets,
+         * TCP_CLOSE (7) for unconnected ones.
+         * Only register ESTABLISHED — unconnected (CLOSE) is the
+         * default state and not useful to display.
+         */
+        (void)enter_IPstate(ctx, "UDP", "ESTABLISHED", TCP_ESTABLISHED);
+        (void)enter_IPstate(ctx, "UDP", (char *)NULL, 0);
+    }
 }
 
 /*

lib/dialects/linux/tests/case-20-udp-socket-state.bash

@@ -0,0 +1,44 @@
+#!/bin/bash
+source tests/common.bash
+
+if [ -z "$(nc -h 2>&1 | grep '\s\-4')" ]; then
+    echo "nc does not support -4 option, skipping" >> $report
+    exit 77
+fi
+
+if [ -z "$(nc -h 2>&1 | grep '\s\-u')" ]; then
+    echo "nc does not support -u option, skipping" >> $report
+    exit 77
+fi
+
+# Use sleep as stdin to keep nc alive without flooding data.
+# /dev/zero causes "Message too long" with ncat (nmap) on UDP.
+sleep 60 | nc -l -u -4 127.0.0.1 10001 > /dev/null &
+server=$!
+sleep 1
+sleep 60 | nc -u -4 127.0.0.1 10001 > /dev/null &
+client=$!
+
+sleep 1
+
+killBoth()
+{
+    kill -9 $1
+    sleep 1
+    kill -9 $2
+} 2> /dev/null > /dev/null
+
+fclient=/tmp/${name}-client-$$
+$lsof -n -P -p $client -a -i UDP > $fclient
+if ! cat $fclient | grep -q "UDP.*127.0.0.1:.*->127.0.0.1:10001 (ESTABLISHED)"; then
+    echo "connected UDP socket missing ESTABLISHED state" >> $report
+    cat $fclient >> $report
+    killBoth $client $server
+    rm -f $fclient
+    exit 1
+fi
+
+rm -f $fclient
+killBoth $client $server
+
+exit 0

src/dialects/linux/dprint.c

@@ -77,15 +77,25 @@ void print_tcptpi(struct lsof_context *ctx, /* context */
         print_unix(ctx, nl);
         return;
     }
-    if ((Ftcptpi & TCPTPI_STATE) && Lf->lts.type == 0) {
+    if ((Ftcptpi & TCPTPI_STATE) && Lf->lts.type >= 0) {
         if (!TcpSt)
             (void)build_IPstates(ctx);
-        if ((s = Lf->lts.state.i + TcpStOff) < 0 || s >= TcpNstates) {
-            (void)snpf(buf, sizeof(buf), "UNKNOWN_TCP_STATE_%d",
-                       Lf->lts.state.i);
-            cp = buf;
-        } else
-            cp = TcpSt[s];
+        switch (Lf->lts.type) {
+        case 0: /* TCP */
+            if ((s = Lf->lts.state.i + TcpStOff) < 0 || s >= TcpNstates) {
+                (void)snpf(buf, sizeof(buf), "UNKNOWN_TCP_STATE_%d",
+                           Lf->lts.state.i);
+                cp = buf;
+            } else
+                cp = TcpSt[s];
+            break;
+        case 1: /* UDP */
+            if (!UdpSt)
+                (void)build_IPstates(ctx);
+            if ((s = Lf->lts.state.i + UdpStOff) >= 0 && s < UdpNstates)
+                cp = UdpSt[s];
+            break;
+        }
         if (cp) {
             if (Ffield)
                 (void)printf("%cST=%s%c", LSOF_FID_TCPTPI, cp, Terminator);

src/print.c

@@ -2001,16 +2001,28 @@ static void json_print_file(struct lsof_context *ctx, int *sep) {
         printf("\"tcp_info\":{");
         int tsep = 0;
 
-        if ((Ftcptpi & TCPTPI_STATE) && Lf->lts.type == 0) {
+        if ((Ftcptpi & TCPTPI_STATE) && Lf->lts.type >= 0) {
             if (!TcpNstates)
                 (void)build_IPstates(ctx);
             int s = Lf->lts.state.i;
-            if (s >= 0 && s < TcpNstates && TcpSt[s])
-                json_print_str(&tsep, "state", TcpSt[s]);
-            else {
-                snprintf(buf, sizeof(buf), "UNKNOWN_%d", s);
-                json_print_str(&tsep, "state", buf);
+            char *st = NULL;
+            if (Lf->lts.type == 0) { /* TCP */
+                int si = s + TcpStOff;
+                if (si >= 0 && si < TcpNstates)
+                    st = TcpSt[si];
+                if (!st) {
+                    snprintf(buf, sizeof(buf), "UNKNOWN_TCP_STATE_%d", s);
+                    st = buf;
+                }
+            } else if (Lf->lts.type == 1) { /* UDP */
+                if (!UdpSt)
+                    (void)build_IPstates(ctx);
+                int si = s + UdpStOff;
+                if (si >= 0 && si < UdpNstates)
+                    st = UdpSt[si];
             }
+            if (st)
+                json_print_str(&tsep, "state", st);
         }
 #if defined(HASTCPTPIQ)
         if (Ftcptpi & TCPTPI_QUEUES) {