On 02/17/2015 02:29 AM, Alan Fisher wrote:
Larry,
I am guessing that you have an RTL8188CE, which uses rtl8192ce.
Yep, my wireless card is an RTL8188CE
The purpose of rtl_is_special_data() is to ensure that management packets have
the highest probability of being successfully transmitted by sending them at a
low rate.
...
It also occurs to me that mac80211 probably handles this function, and that it
may be possible to remove this routine, which is essentially what your
workaround does.
I couldn't find any information on mac80211 treating certain packets (ARP, DHCP,
etc...) as special. It does seem to handle automatic rate selection, though. I
would think that would be enough to handle packet loss reasonably well. I
believe the protocols tested for here all have mechanisms for handling lost
packets. I also can't find any other 802.11 drivers which try to handle DHCP
packets in a special way. I think it would be safe to remove this routine. I
have a patch to do that, if you're okay with that change.
The story is a bit more complicated. These drivers use firmware rate selection,
not the ones in mac80211. At this point, I would not be comfortable with
removing the entire routine.
Regarding the patch, this change:
- } else if (0x86DD == ether_type) {
- return true;
}
successfully prevents IPv6 packets from being treated as special (and thus
dropped).
However, this:
+ if (ETH_P_IP == ether_type || ETH_P_IPV6 == ether_type) {
ip = (struct iphdr *)((u8 *)skb->data + offset +
seems to be reading an IPv4 header (struct iphdr) from an IPv6 packet. I believe
a struct ipv6hdr should be used here.
You are correct. My patch was prepared too hastily.
If we are to continue handling certain types of packets differently, IPv6
neighbor solicitation messages (like ARP in IPv4) and IPv6 router discovery
messages (stateless IPv6 autoconfig, similar to DHCP in IPv4 networks) should
probably be added to the list to maintain consistency with what is being handled
for IPv4. These are both variants of ICMPv6 packets, although generally
transmitting all ICMPv6 packets at the lowest rate is probably a bad idea, as
ICMP echo is commonly used to measure network performance and should be treated
the same as normal traffic.
For the moment, I think we need to return false, not true, for all IPv6 packets
until a more complete solution is found. Does the attached patch fix the problem
you are seeing? I do not have an IPv6 compliant ISP, thus I cannot do much testing.
Larry
Index: wireless-drivers-next/drivers/net/wireless/rtlwifi/base.c
===================================================================
--- wireless-drivers-next.orig/drivers/net/wireless/rtlwifi/base.c
+++ wireless-drivers-next/drivers/net/wireless/rtlwifi/base.c
@@ -1386,8 +1386,11 @@ u8 rtl_is_special_data(struct ieee80211_
}
return true;
- } else if (0x86DD == ether_type) {
- return true;
+ } else if (ETH_P_IPV6 == ether_type) {
+ /* TODO: Handle any IPv6 cases that need special handling.
+ * For now, always return false
+ */
+ goto end;
}
end:
