To reproduce:

* Install fresh Fedora 34 VM
* Compile Bitcoin Core and run `./test/functional/p2p_dns_seeds.py`
{
        allowed_syscalls.insert(__NR_brk);     
        allowed_syscalls.insert(__NR_madvise); 
        allowed_syscalls.insert(__NR_membarrier); 
        allowed_syscalls.insert(__NR_mlock);    
        allowed_syscalls.insert(__NR_mmap);     
        allowed_syscalls.insert(__NR_mprotect); 
        allowed_syscalls.insert(__NR_munlock);  
        allowed_syscalls.insert(__NR_munmap);   
    }
    void AllowEpoll()
    {
        allowed_syscalls.insert(__NR_epoll_create1); 
        allowed_syscalls.insert(__NR_epoll_ctl);     
        allowed_syscalls.insert(__NR_epoll_pwait);   
        allowed_syscalls.insert(__NR_epoll_wait);    
    }
    void AllowEventFd()
    {
        allowed_syscalls.insert(__NR_eventfd2); 
    }
    void AllowFileSystem()