Fix "podman run port forward range" flake

The test must ensure that all ports in the range are free not just
the first. This flakes often because port 5355 is always in use by
systemd-resolved on fedora.

Fixes #14716

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

test/system/150-login.bats

@@ -314,7 +314,7 @@ function _test_skopeo_credential_sharing() {
     fi
 
     # Make sure socket is closed
-    if { exec 3<> /dev/tcp/127.0.0.1/${PODMAN_LOGIN_REGISTRY_PORT}; } &>/dev/null; then
+    if ! port_is_free $PODMAN_LOGIN_REGISTRY_PORT; then
         die "Socket still seems open"
     fi
 }

test/system/500-networking.bats

@@ -676,12 +676,12 @@ EOF
 
 @test "podman run port forward range" {
     for netmode in bridge slirp4netns:port_handler=slirp4netns slirp4netns:port_handler=rootlesskit; do
-        local port=$(random_free_port)
-        local end_port=$(( $port + 2 ))
-        local range="$port-$end_port:$port-$end_port"
+        local range=$(random_free_port_range 3)
+        local port="${test%-*}"
+        local end_port="${test#-*}"
         local random=$(random_string)
 
-        run_podman run --network $netmode -p "$range" -d $IMAGE sleep inf
+        run_podman run --network $netmode -p "$range:$range" -d $IMAGE sleep inf
         cid="$output"
         for port in $(seq $port $end_port); do
             run_podman exec -d $cid nc -l -p $port -e /bin/cat

test/system/helpers.bash

@@ -284,7 +284,7 @@ function random_free_port() {
 
     local port
     for port in $(shuf -i ${range}); do
-        if ! { exec {unused_fd}<> /dev/tcp/127.0.0.1/$port; } &>/dev/null; then
+        if port_is_free $port; then
             echo $port
             return
         fi
@@ -293,6 +293,35 @@ function random_free_port() {
     die "Could not find open port in range $range"
 }
 
+function random_free_port_range() {
+    local size=${1?Usage: random_free_port_range SIZE (as in, number of ports)}
+
+    local maxtries=10
+    while [[ $maxtries -gt 0 ]]; do
+        local firstport=$(random_free_port)
+        local all_ports_free=1
+        for i in $(seq 2 $size); do
+            if ! port_is_free $((firstport + $i)); then
+                all_ports_free=
+                break
+            fi
+        done
+        if [[ -n "$all_ports_free" ]]; then
+            echo "$firstport-$((firstport + $size - 1))"
+            return
+        fi
+
+        maxtries=$((maxtries - 1))
+    done
+
+    die "Could not find free port range with size $size"
+}
+
+function port_is_free() {
+     local port=${1?Usage: port_is_free PORT}
+    ! { exec {unused_fd}<> /dev/tcp/127.0.0.1/$port; } &>/dev/null
+}
+
 ###################
 #  wait_for_port  #  Returns once port is available on host
 ###################