New submission from Марк Коренберг <socketp...@gmail.com>:
https://github.com/python/cpython/pull/4724 `recvfrom` from multicast socket is painfull slow. In fact, it returns sender address in form: `('fe80::941f:f6ff:fe04:c560%qwe', 42133, 0, 78)` which is superfluous, since interface-name part (`%qwe`) is not actually used. Actually, scopeid (`78`) signify interface/scope/zone_id. This tuple can be used for `.sendto()` either with this interface-name-part or without. The problem is in the performance. For each `recvrfom()`, `getnameinfo()` internally converts interface index to interface name using three syscalls, i.e. `socket(), getsockopt()?, close()` , which slows down receiving (I have not measured result, but see additional syscalls in `strace`). In order to convert from tuple to string-based full address one may use `getnameinfo()`: As you can see, initial interface is ignored (but without my patch it is also validated uselessly): ``` In[1]: socket.getnameinfo(('fe80::941f:f6ff:fe04:c560%qwe', 42133, 0, 78), socket.NI_NUMERICHOST) Out[1]: ('fe80::941f:f6ff:fe04:c560%qwe', '42133') In[2]: socket.getnameinfo(('fe80::941f:f6ff:fe04:c560', 42133, 0, 78), socket.NI_NUMERICHOST) Out[2]: ('fe80::941f:f6ff:fe04:c560%qwe', '42133') ``` ---------- components: Library (Lib) messages: 307651 nosy: socketpair priority: normal severity: normal status: open title: Converting ipv6 address to string representation using getnameinfo() is wrong. type: performance versions: Python 3.6, Python 3.7, Python 3.8 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue32221> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
