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

service/process/process_linux.go

@@ -0,0 +1,96 @@
+package process
+
+import (
+	"context"
+	"fmt"
+	"syscall"
+
+	"github.com/safing/portbase/log"
+)
+
+const (
+	// SystemProcessID is the PID of the System/Kernel itself.
+	SystemProcessID = 0
+
+	// SystemInitID is the PID of the system init process.
+	SystemInitID = 1
+)
+
+// FindProcessGroupLeader returns the process that leads the process group.
+// Returns nil when process ID is not valid (or virtual).
+// If the process group leader is found, it is set on the process.
+// If that process does not exist anymore, then the highest existing parent process is returned.
+// If an error occurs, the best match is set.
+func (p *Process) FindProcessGroupLeader(ctx context.Context) error {
+	p.Lock()
+	defer p.Unlock()
+
+	// Return the leader if we already have it.
+	if p.leader != nil {
+		return nil
+	}
+
+	// Check if we have the process group leader PID.
+	if p.LeaderPid == UndefinedProcessID {
+		return nil
+	}
+
+	// Return nil if we already are the leader.
+	if p.LeaderPid == p.Pid {
+		return nil
+	}
+
+	// Get process leader process.
+	leader, err := GetOrFindProcess(ctx, p.LeaderPid)
+	if err == nil {
+		p.leader = leader
+		log.Tracer(ctx).Debugf("process: found process leader of %d: pid=%d pgid=%d", p.Pid, leader.Pid, leader.LeaderPid)
+		return nil
+	}
+
+	// If we can't get the process leader process, it has likely already exited.
+	// In that case, find the highest existing parent process within the process group.
+	var (
+		nextParentPid = p.ParentPid
+		lastParent    *Process
+	)
+	for {
+		// Get next parent.
+		parent, err := GetOrFindProcess(ctx, nextParentPid)
+		if err != nil {
+			p.leader = lastParent
+			return fmt.Errorf("failed to find parent %d: %w", nextParentPid, err)
+		}
+
+		// Check if we are ready to return.
+		switch {
+		case parent.Pid == p.LeaderPid:
+			// Found the process group leader!
+			p.leader = parent
+			return nil
+
+		case parent.LeaderPid != p.LeaderPid:
+			// We are leaving the process group. Return the previous parent.
+			p.leader = lastParent
+			log.Tracer(ctx).Debugf("process: found process leader (highest parent) of %d: pid=%d pgid=%d", p.Pid, parent.Pid, parent.LeaderPid)
+			return nil
+
+		case parent.ParentPid == SystemProcessID,
+			parent.ParentPid == SystemInitID:
+			// Next parent is system or init.
+			// Use current parent.
+			p.leader = parent
+			log.Tracer(ctx).Debugf("process: found process leader (highest parent) of %d: pid=%d pgid=%d", p.Pid, parent.Pid, parent.LeaderPid)
+			return nil
+		}
+
+		// Check next parent.
+		lastParent = parent
+		nextParentPid = parent.ParentPid
+	}
+}
+
+// GetProcessGroupID returns the process group ID of the given PID.
+func GetProcessGroupID(ctx context.Context, pid int) (int, error) {
+	return syscall.Getpgid(pid)
+}