classification
Title: socket.bind to AF_PACKET should use passed interface name
Type: Stage:
Components: Versions:
process
Status: closed Resolution:
Dependencies: Superseder:
Assigned To: Nosy List: mturon
Priority: normal Keywords:

Created on 2016-10-27 18:14 by mturon, last changed 2016-10-28 07:06 by mturon. This issue is now closed.

Messages (3)
msg279558 - (view) Author: Martin Turon (mturon) Date: 2016-10-27 18:14
When binding to AF_PACKET linux kernel sockets, the interface name is not passed in when given -- it is always "".  This causes problems, for example, receiving packets to a "monitor0" interface doesn't work.

diff -r a6548e230ed6 Modules/socketmodule.c
--- a/Modules/socketmodule.c    Thu Oct 27 19:33:22 2016 +0300
+++ b/Modules/socketmodule.c    Thu Oct 27 11:13:12 2016 -0700
@@ -1344,6 +1344,7 @@
     {
         struct sockaddr_ll *a = (struct sockaddr_ll *)addr;
         char *ifname = "";
+        // ^^ ifname should be set to interface name passed in via sockaddr.
         struct ifreq ifr;
         /* need to look up interface name give index */
         if (a->sll_ifindex) {
msg279562 - (view) Author: Martin Turon (mturon) Date: 2016-10-27 18:43
Just for clarity, the high level bug is that when binding to an interface using AF_PACKET, transmissions work, but receive does not:

    sock = socket.socket(socket.AF_PACKET, socket.SOCK_RAW, ETH_P_IEEE802154)
    sock.bind(("monitor0", ETH_P_IEEE802154))

    sock.send(test_frame)   # transmission works fine
    pkt = sock.recv(127)    # never receives, though C test works fine

The same test written in C that calls ioctl(sockfd, SIOCGIFNAME, &ifr) to lookup ifindex for bind from ifname="monitor0" works fine.
msg279587 - (view) Author: Martin Turon (mturon) Date: 2016-10-28 07:06
If I bind to port 0, it works for both tx and rx.  Sorry for the false alarm!

sock.bind(("monitor0", 0))
History
Date User Action Args
2016-10-28 07:06:10mturonsetstatus: open -> closed

messages: + msg279587
2016-10-27 18:43:42mturonsetmessages: + msg279562
2016-10-27 18:14:58mturoncreate