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|
package internal
import (
"errors"
"fmt"
"os"
"path/filepath"
"strconv"
"sync"
"syscall"
)
type commResolver struct {
comms map[uint32]string
mu sync.RWMutex
pending map[uint32]struct{}
closed bool
lookupQueue chan uint32
lookupWorkers int
resolveFn func(uint32) (string, error)
warningFn func(string)
startWorkersOnce sync.Once
workersWG sync.WaitGroup
shutdownOnce sync.Once
}
func newCommResolver(comms map[uint32]string) *commResolver {
if comms == nil {
comms = make(map[uint32]string)
}
r := &commResolver{
comms: comms,
pending: make(map[uint32]struct{}),
}
r.ensureLookupConfig()
return r
}
func (r *commResolver) ensureLookupConfig() {
if r.lookupWorkers <= 0 {
r.lookupWorkers = defaultCommLookupWorkers
}
if r.lookupQueue == nil {
r.lookupQueue = make(chan uint32, defaultCommLookupQueueSize)
}
if r.resolveFn == nil {
r.resolveFn = resolveCommFromProcWithError
}
}
func (r *commResolver) startLookupWorkers() {
r.ensureLookupConfig()
r.mu.RLock()
closed := r.closed
r.mu.RUnlock()
if closed {
return
}
r.startWorkersOnce.Do(func() {
for i := 0; i < r.lookupWorkers; i++ {
r.workersWG.Add(1)
go r.lookupWorker()
}
})
}
func (r *commResolver) lookupWorker() {
defer r.workersWG.Done()
for tid := range r.lookupQueue {
comm, err := r.resolveFn(tid)
r.mu.Lock()
delete(r.pending, tid)
if comm != "" {
r.comms[tid] = comm
}
r.mu.Unlock()
r.notifyResolveFailure(tid, err)
}
}
func (r *commResolver) seedTrackedPidComm(pidFilter int) {
candidates := []uint32{uint32(os.Getpid()), uint32(os.Getppid())}
if pidFilter > 0 {
candidates = append(candidates, uint32(pidFilter))
}
seen := make(map[uint32]struct{}, len(candidates))
for _, tid := range candidates {
if tid == 0 {
continue
}
if _, ok := seen[tid]; ok {
continue
}
seen[tid] = struct{}{}
comm, err := r.resolveFn(tid)
if comm != "" {
r.setCached(tid, comm)
continue
}
r.notifyResolveFailure(tid, err)
r.queueLookup(tid)
}
}
func (r *commResolver) comm(tid uint32) string {
if comm, ok := r.cached(tid); ok {
return comm
}
r.queueLookup(tid)
return ""
}
func (r *commResolver) cached(tid uint32) (string, bool) {
r.mu.RLock()
defer r.mu.RUnlock()
comm, ok := r.comms[tid]
return comm, ok
}
func (r *commResolver) setCached(tid uint32, comm string) {
if comm == "" {
return
}
r.mu.Lock()
r.comms[tid] = comm
r.mu.Unlock()
}
func (r *commResolver) queueLookup(tid uint32) {
if tid == 0 {
return
}
r.startLookupWorkers()
r.mu.Lock()
defer r.mu.Unlock()
if r.closed {
return
}
if _, ok := r.comms[tid]; ok {
return
}
if r.pending == nil {
r.pending = make(map[uint32]struct{})
}
if _, ok := r.pending[tid]; ok {
return
}
r.pending[tid] = struct{}{}
// Keep event processing non-blocking if resolver workers are saturated.
select {
case r.lookupQueue <- tid:
default:
delete(r.pending, tid)
}
}
func (r *commResolver) shutdown() {
r.shutdownOnce.Do(func() {
r.ensureLookupConfig()
r.mu.Lock()
r.closed = true
for tid := range r.pending {
delete(r.pending, tid)
}
queue := r.lookupQueue
r.mu.Unlock()
close(queue)
r.workersWG.Wait()
})
}
func (r *commResolver) notifyResolveFailure(tid uint32, err error) {
if err == nil {
return
}
r.notifyWarning(fmt.Sprintf("failed to resolve comm for tid %d: %v", tid, err))
}
func (r *commResolver) notifyWarning(message string) {
if r.warningFn == nil || message == "" {
return
}
r.warningFn(message)
}
func (e *eventLoop) shutdownCommResolver() {
if e.commResolver == nil {
return
}
e.commResolver.shutdown()
}
func (e *eventLoop) comm(tid uint32) string {
return e.commState().comm(tid)
}
func (e *eventLoop) cachedComm(tid uint32) (string, bool) {
return e.commState().cached(tid)
}
func (e *eventLoop) setCachedComm(tid uint32, comm string) {
e.commState().setCached(tid, comm)
}
func (e *eventLoop) queueCommLookup(tid uint32) {
e.commState().queueLookup(tid)
}
func procTidPathPrefix(tid uint32) string {
return "/proc/" + strconv.FormatUint(uint64(tid), 10)
}
func resolveCommFromProc(tid uint32) string {
comm, _ := resolveCommFromProcWithError(tid)
return comm
}
func resolveCommFromProcWithError(tid uint32) (string, error) {
procPath := procTidPathPrefix(tid)
commPath := procPath + "/comm"
data, commErr := os.ReadFile(commPath)
if commErr == nil {
comm := string(data)
if len(comm) > 0 && comm[len(comm)-1] == '\n' {
comm = comm[:len(comm)-1]
}
if comm != "" {
return comm, nil
}
} else if isTransientProcError(commErr) {
commErr = nil
} else {
commErr = fmt.Errorf("read %s: %w", commPath, commErr)
}
exePath := procPath + "/exe"
linkName, linkErr := os.Readlink(exePath)
if linkErr == nil {
if base := filepath.Base(linkName); base != "" {
return base, nil
}
} else if isTransientProcError(linkErr) {
linkErr = nil
} else {
linkErr = fmt.Errorf("readlink %s: %w", exePath, linkErr)
}
return "", errors.Join(commErr, linkErr)
}
func isTransientProcError(err error) bool {
return errors.Is(err, os.ErrNotExist) || errors.Is(err, syscall.ENOENT) || errors.Is(err, syscall.ESRCH)
}
|
