wip: migrate to mono-repo. SPN has already been moved to spn/

service/network/proc/findpid.go

@@ -0,0 +1,107 @@
+//go:build linux
+
+package proc
+
+import (
+	"errors"
+	"io/fs"
+	"os"
+	"strconv"
+
+	"github.com/safing/portbase/log"
+	"github.com/safing/portmaster/service/network/socket"
+)
+
+// GetPID returns the already existing pid of the given socket info or searches for it.
+// This also acts as a getter for socket.Info.PID, as locking for that occurs here.
+func GetPID(socketInfo socket.Info) (pid int) {
+	// Get currently assigned PID to the socket info.
+	currentPid := socketInfo.GetPID()
+
+	// If the current PID already is valid (ie. not unidentified), return it immediately.
+	if currentPid != socket.UndefinedProcessID {
+		return currentPid
+	}
+
+	// Find PID for the given UID and inode.
+	pid = findPID(socketInfo.GetUIDandInode())
+
+	// Set the newly found PID on the socket info.
+	socketInfo.SetPID(pid)
+
+	// Return found PID.
+	return pid
+}
+
+// findPID returns the pid of the given uid and socket inode.
+func findPID(uid, inode int) (pid int) {
+	socketName := "socket:[" + strconv.Itoa(inode) + "]"
+
+	// Always update pid table (it has a call limiter anyway)
+	updatePids()
+
+	// Get all pids for the given uid.
+	pids, ok := getPidsByUser(uid)
+	if !ok {
+		return socket.UndefinedProcessID
+	}
+
+	// Look through the PIDs in reverse order, because higher/newer PIDs will be more likely to
+	// be searched for.
+	for j := len(pids) - 1; j >= 0; j-- {
+		if pidHasSocket(pids[j], socketName) {
+			return pids[j]
+		}
+	}
+
+	return socket.UndefinedProcessID
+}
+
+func pidHasSocket(pid int, socketName string) bool {
+	socketBase := "/proc/" + strconv.Itoa(pid) + "/fd"
+	entries := readDirNames(socketBase)
+	if len(entries) == 0 {
+		return false
+	}
+
+	socketBase += "/"
+	// Look through the FDs in reverse order, because higher/newer FDs will be
+	// more likely to be searched for.
+	for i := len(entries) - 1; i >= 0; i-- {
+		link, err := os.Readlink(socketBase + entries[i])
+		if err != nil {
+			if !errors.Is(err, fs.ErrNotExist) {
+				log.Warningf("proc: failed to read link /proc/%d/fd/%s: %s", pid, entries[i], err)
+			}
+			continue
+		}
+		if link == socketName {
+			return true
+		}
+	}
+
+	return false
+}
+
+// readDirNames only reads the directory names. Using os.ReadDir() would call `lstat` on every
+// resulting directory name, which we don't need. This function will be called a lot, so we should
+// refrain from unnecessary work.
+func readDirNames(dir string) (names []string) {
+	file, err := os.Open(dir)
+	if err != nil {
+		if !errors.Is(err, fs.ErrNotExist) {
+			log.Warningf("proc: could not open directory %s: %s", dir, err)
+		}
+		return
+	}
+	defer func() {
+		_ = file.Close()
+	}()
+
+	names, err = file.Readdirnames(0)
+	if err != nil {
+		log.Warningf("proc: could not get entries from directory %s: %s", dir, err)
+		return []string{}
+	}
+	return
+}