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Attempt to use PID namespace to control process with timeout, while ensuring child cleanup
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| #!/bin/bash | |
| waitPortOpen() { | |
| local host=$1 | |
| local port=$2 | |
| local timeoutSeconds=$3 | |
| local intervalSeconds=$4 | |
| local connectTimeoutSeconds=$5 | |
| if [[ -z "$intervalSeconds" ]]; then | |
| intervalSeconds=0.5 | |
| fi | |
| if [[ -z "$connectTimeoutSeconds" ]]; then | |
| connectTimeoutSeconds=1.0 | |
| fi | |
| local semaphoreDir | |
| semaphoreDir=$(mktemp -d) | |
| if [[ -z "$semaphoreDir" ]]; then | |
| return 1 | |
| fi | |
| local timeoutPid | |
| # Note: If bash -c is run with a command that doesn't require Bash (e.g., sleep 1), it apparently execs | |
| # that command, defeating our purpose of having bash = PID 1, sleep = PID 2; we add the >/dev/null redirect | |
| # for this reason. | |
| read -r timeoutPid < <( | |
| unshare -pUf --mount-proc \ | |
| bash -c "sleep $timeoutSeconds >/dev/null" 2>/dev/null & | |
| pgrep --parent $! | |
| ) | |
| (exec 2>/dev/null; nsenter -t "$timeoutPid" --preserve-credentials -U -m -p bash <<-EOF | |
| while true; do | |
| # nmap commands are allowed to overlap when connectTimeoutSeconds is greater than intervalSeconds. For | |
| # example, with connectTimeoutSeconds=1.0 and intervalSeconds=0.25, we would expect up to four nmap | |
| # processes running concurrently. | |
| nmap -n -Pn -p "$port" \ | |
| --min-rtt-timeout "$connectTimeoutSeconds"s \ | |
| --max-rtt-timeout "$connectTimeoutSeconds"s \ | |
| --max-retries 0 \ | |
| -oG /dev/stdout '$host' 2>/dev/null | | |
| grep -Fq 'Ports: $port/open' && touch "$semaphoreDir/up" && kill -9 2 & | |
| sleep "$intervalSeconds" | |
| done | |
| EOF | |
| ) | |
| if [[ -e "$semaphoreDir/up" ]]; then | |
| rm -rf "$semaphoreDir" | |
| return 0 | |
| fi | |
| rm -rf "$semaphoreDir" | |
| return 1 | |
| } | |
| waitPortOpen "$@" |
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