Zgrab2 is getting stuck intermittently while doing tls on port 443

[NishantG01]

I am running the command zgrab2 zgrab2 -f bhQ5Temp tls -p 443 -t 20 Ideally, zgrab2 should timeout after some time, but it's not happening. Need help in diagnosing the issue, as a first step I recorded the below output from perf tool and strace tool Please check the zgrab2 stack as recorded with perf-tool `Samples: 79 of event 'cpu-clock', Event count (approx.): 19750000 Children Self Command Shared Object Symbol ▒

• 84.81% 0.00% zgrab2 zgrab2 [.] runtime.goexit ▒
• runtime.goexit ▒
  • 69.62% runtime.systemstack ▒ runtime.gcBgMarkWorker.func2 ◆
    • runtime.gcDrain ▒
      • 45.57% runtime.scanobject ▒ 10.13% runtime.findObject ▒ 6.33% runtime.greyobject ▒
        • 1.27% apic_timer_interrupt ▒ smp_apic_timer_interrupt ▒ irq_exit ▒ do_softirq ▒ call_softirq ▒ __do_softirq ▒ run_timer_softirq ▒
      • 22.78% runtime.markroot ▒
        • 11.39% runtime.markroot.func1 ▒
          • runtime.scanstack ▒
            • 7.59% runtime.gentraceback ▒
              • 5.06% runtime.scanstack.func1 ▒
                • runtime.scanframeworker ▒ 2.53% runtime.(*stackScanState).addObject ▒ 1.27% runtime.getStackMap ▒
                  • 1.27% runtime.scanblock ▒ runtime.findObject ▒ 1.27% runtime.findfunc ▒
            • 2.53% runtime.shrinkstack ▒ runtime.findfunc ▒ 1.27% runtime.findfunc ▒
        • 8.86% runtime.markrootBlock ▒
          • runtime.scanblock ▒
            • 2.53% runtime.greyobject ▒ runtime.(*gcWork).put ▒ runtime.(*gcWork).init ▒ runtime.getempty ▒ runtime.getempty.func1 ▒ runtime.(*mheap).allocManual ▒
              • runtime.(*mheap).allocSpan ▒
                • 1.27% runtime.(*pageCache).alloc ▒ runtime.findBitRange64 ▒ 1.27% runtime.(*pageAlloc).allocRange ▒ 1.27% runtime.(*gcWork).put ▒ 1.27% runtime.findObject ▒ 2.53% runtime.markrootSpans ▒
  • 6.33% runtime.forcegchelper ▒
    • runtime.systemstack ▒
  • 3.80% runtime.bgsweep ▒
  • 2.53% runtime.mcall ▒
  • 2.53% runtime.gcBgMarkWorker `

strace output --- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=14868, si_uid=1002} --- rt_sigreturn({mask=[]}) = 14868 tgkill(14868, 14873, SIGURG) = 0 futex(0x1243f68, FUTEX_WAIT_PRIVATE, 0, NULL) = -1 EAGAIN (Resource temporarily unavailable) futex(0x1243710, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0x12435f8, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0xc000608148, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0x1243f68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0 epoll_pwait(14, [], 128, 0, NULL, 3312989) = 0 futex(0x12436f8, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0x12435f8, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0xc000608148, FUTEX_WAKE_PRIVATE, 1) = 1 sched_yield() = 0 futex(0x125b2e0, FUTEX_WAKE_PRIVATE, 1) = 0 getpid() = 14868 tgkill(14868, 14874, SIGURG) = 0 getpid() = 14868 --- SIGURG {si_signo=SIGURG, si_code=SI_TKILL, si_pid=14868, si_uid=1002} --- rt_sigreturn({mask=[]}) = 14868 tgkill(14868, 14874, SIGURG) = 0 futex(0xc00018e148, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0x1243710, FUTEX_WAIT_PRIVATE, 0, {0, 100000}) = -1 EAGAIN (Resource temporarily unavailable) epoll_pwait(14, [], 128, 0, NULL, 3312989) = 0 futex(0x12436f8, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0x12435f8, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0xc00018e148, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0x1243710, FUTEX_WAIT_PRIVATE, 0, {0, 100000}) = 0 futex(0x1243f68, FUTEX_WAIT_PRIVATE, 0, NULL) = 0 epoll_pwait(14, [], 128, 0, NULL, 3313109) = 0 futex(0x12436f8, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0x12435f8, FUTEX_WAKE_PRIVATE, 1) = 1 futex(0xc00018e148, FUTEX_WAKE_PRIVATE, 1) = 1 sched_yield() = 0 futex(0x125b2e0, FUTEX_WAKE_PRIVATE, 1) = 0 getpid() = 14868 tgkill(14868, 14875, SIGURG) = 0

[NishantG01]

Please find the complete stack trace from perf tool

• 84.81% 0.00% zgrab2 zgrab2 [.] runtime.goexit
• 77.22% 0.00% zgrab2 zgrab2 [.] runtime.systemstack
• 69.62% 0.00% zgrab2 zgrab2 [.] runtime.gcBgMarkWorker.func2
• 69.62% 1.27% zgrab2 zgrab2 [.] runtime.gcDrain
• 46.84% 27.85% zgrab2 zgrab2 [.] runtime.scanobject
• 22.78% 0.00% zgrab2 zgrab2 [.] runtime.markroot
• 12.66% 12.66% zgrab2 zgrab2 [.] runtime.findObject
• 12.66% 0.00% zgrab2 [unknown] [.] 0x18e92d244cb60f08
• 12.66% 0.00% zgrab2 [unknown] [.] 0x000000c000038800
• 12.66% 0.00% zgrab2 zgrab2 [.] runtime.clone
• 12.66% 0.00% zgrab2 zgrab2 [.] runtime.mstart
• 12.66% 0.00% zgrab2 zgrab2 [.] runtime.mstart1
• 12.66% 0.00% zgrab2 zgrab2 [.] runtime.sysmon
• 11.39% 0.00% zgrab2 zgrab2 [.] runtime.markroot.func1
• 11.39% 0.00% zgrab2 zgrab2 [.] runtime.scanstack
• 10.13% 6.33% zgrab2 zgrab2 [.] runtime.futex
• 10.13% 3.80% zgrab2 zgrab2 [.] runtime.scanblock
• 8.86% 6.33% zgrab2 zgrab2 [.] runtime.greyobject
• 8.86% 0.00% zgrab2 [kernel.kallsyms] [k] system_call_fastpath
• 8.86% 0.00% zgrab2 zgrab2 [.] runtime.markrootBlock
• 7.59% 1.27% zgrab2 zgrab2 [.] runtime.gentraceback
• 7.59% 1.27% zgrab2 zgrab2 [.] runtime.notetsleep_internal
• 7.59% 0.00% zgrab2 zgrab2 [.] runtime.notetsleep
• 6.33% 0.00% zgrab2 zgrab2 [.] runtime.forcegchelper
• 5.06% 5.06% zgrab2 zgrab2 [.] runtime.gcResetMarkState
• 5.06% 0.00% zgrab2 zgrab2 [.] runtime.scanstack.func1
• 5.06% 0.00% zgrab2 zgrab2 [.] runtime.scanframeworker
• 3.80% 3.80% zgrab2 [kernel.kallsyms] [k] _raw_spin_unlock_irqrestore
• 3.80% 3.80% zgrab2 [kernel.kallsyms] [k] finish_task_switch
• 3.80% 3.80% zgrab2 zgrab2 [.] runtime.findfunc
• 3.80% 1.27% zgrab2 zgrab2 [.] runtime.(*gcWork).put
• 3.80% 0.00% zgrab2 zgrab2 [.] runtime.mcall
• 3.80% 0.00% zgrab2 [kernel.kallsyms] [k] sys_futex
• 3.80% 0.00% zgrab2 [kernel.kallsyms] [k] do_futex
• 3.80% 0.00% zgrab2 zgrab2 [.] runtime.usleep
• 3.80% 0.00% zgrab2 [kernel.kallsyms] [k] sys_nanosleep
• 3.80% 0.00% zgrab2 [kernel.kallsyms] [k] hrtimer_nanosleep
• 3.80% 0.00% zgrab2 [kernel.kallsyms] [k] do_nanosleep
• 3.80% 0.00% zgrab2 [kernel.kallsyms] [k] schedule
• 3.80% 0.00% zgrab2 [kernel.kallsyms] [k] __schedule
• 3.80% 0.00% zgrab2 zgrab2 [.] runtime.bgsweep
• 3.80% 0.00% zgrab2 zgrab2 [.] runtime.sweepone
• 2.53% 2.53% zgrab2 zgrab2 [.] runtime.(*stackScanState).addObject
• 2.53% 2.53% zgrab2 zgrab2 [.] runtime.markrootSpans
• 2.53% 1.27% zgrab2 zgrab2 [.] runtime.(*mspan).sweep
• 2.53% 0.00% zgrab2 zgrab2 [.] runtime.gosched_m
• 2.53% 0.00% zgrab2 zgrab2 [.] runtime.goschedImpl
• 2.53% 1.27% zgrab2 zgrab2 [.] runtime.shrinkstack
• 2.53% 0.00% zgrab2 zgrab2 [.] runtime.(*gcWork).init
• 2.53% 0.00% zgrab2 zgrab2 [.] runtime.(*mheap).allocManual
• 2.53% 0.00% zgrab2 zgrab2 [.] runtime.(*mheap).allocSpan
• 2.53% 0.00% zgrab2 zgrab2 [.] runtime.gcBgMarkWorker
• 2.53% 0.00% zgrab2 zgrab2 [.] runtime.findrunnable