Improve concurrent connection handling support

network/proc/pids_by_user.go

@@ -0,0 +1,82 @@
+package proc
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"sync"
+	"syscall"
+
+	"github.com/safing/portbase/log"
+	"github.com/safing/portbase/utils"
+)
+
+var (
+	// pidsByUserLock is also used for locking the socketInfo.PID on all socket.*Info structs.
+	pidsByUser      = make(map[int][]int)
+	pidsByUserLock  sync.RWMutex
+	fetchPidsByUser utils.OnceAgain
+)
+
+// getPidsByUser returns the cached PIDs for the given UID.
+func getPidsByUser(uid int) (pids []int, ok bool) {
+	pidsByUserLock.RLock()
+	defer pidsByUserLock.RUnlock()
+
+	pids, ok = pidsByUser[uid]
+	return
+}
+
+// updatePids fetches and creates a new pidsByUser map using utils.OnceAgain.
+func updatePids() {
+	fetchPidsByUser.Do(func() {
+		newPidsByUser := make(map[int][]int)
+		pidCnt := 0
+
+		entries := readDirNames("/proc")
+		if len(entries) == 0 {
+			log.Warning("proc: found no PIDs in /proc")
+			return
+		}
+
+	entryLoop:
+		for _, entry := range entries {
+			pid, err := strconv.ParseInt(entry, 10, 32)
+			if err != nil {
+				continue entryLoop
+			}
+
+			statData, err := os.Stat(fmt.Sprintf("/proc/%d", pid))
+			if err != nil {
+				log.Warningf("proc: could not stat /proc/%d: %s", pid, err)
+				continue entryLoop
+			}
+			sys, ok := statData.Sys().(*syscall.Stat_t)
+			if !ok {
+				log.Warningf("proc: unable to parse /proc/%d: wrong type", pid)
+				continue entryLoop
+			}
+
+			pids, ok := newPidsByUser[int(sys.Uid)]
+			if ok {
+				newPidsByUser[int(sys.Uid)] = append(pids, int(pid))
+			} else {
+				newPidsByUser[int(sys.Uid)] = []int{int(pid)}
+			}
+			pidCnt++
+		}
+
+		// Reverse slice orders, because higher PIDs will be more likely to be searched for.
+		for _, slice := range newPidsByUser {
+			for i, j := 0, len(slice)-1; i < j; i, j = i+1, j-1 {
+				slice[i], slice[j] = slice[j], slice[i]
+			}
+		}
+
+		log.Tracef("proc: updated PID table with %d entries", pidCnt)
+
+		pidsByUserLock.Lock()
+		defer pidsByUserLock.Unlock()
+		pidsByUser = newPidsByUser
+	})
+}