XSK destinations maps stay empty

[joelasagne]

Hi, i'm trying to make XSK work on my dev env, but for some reason I can't get the "xsk-destinations-v4" pinned map to get populated.

Here is my config for my sockets/servers (I only kept one newServer to not flood):

local sockets = {}

for i=1,6 do
  xsk = newXsk({ifName="eth4", NIC_queue_id=i-1, frameNums=65536, xskMapPath="/sys/fs/bpf/dnsdist/xskmap"})
  table.insert(sockets, xsk)
  addLocal("192.168.93.212:53", {xskSocket=xsk, reusePort=true})
end

newServer({address="192.168.93.216:53",source="192.168.93.212@eth4", xskSockets=sockets, MACAddr='bc:24:11:90:3a:37', checkName="localhost.", checkType="A"})

The loadbalancing works fine, but never using XDP/XSK, and when I check the pinned maps (bpftool map dump pinned /sys/fs/bpf/dnsdist/xsk-destinations-v4), it's always empty [].

Is there something I'm doing wrong so that dnsdist ignores my servers for XSK ?

[rgacogne]

Hi! Do you execute the xdp.py program (see https://www.dnsdist.org/advanced/xsk.html)?

[joelasagne]

Update, restarted dnsdist after getting the xdp program running, it worked, but not so long after the map went back to being empty again, I'll try understanding why.

[joelasagne]

@rgacogne I've found that i had a cron job script running `dnsdist -e "bpf:getStats()". I disabled it, xsk works perfectly fine, but the xsk-destination-v4 map gets emptied out the moment I run the command in my terminal.

[rgacogne]

I will have to look into exactly what is happening but my guess is that the XSK commands are executed in single-command mode (dnsdist -e) and should not. You might be able to use inClientStartup 1 to work around that in the meantime.

[rgacogne]

So I did find a nasty crash (fixed by #15362) but I have not been able to reproduce the case where the content of the map is overwritten by executing dnsdist -e. I'm guessing your configuration is actually more complex than what you shared, especially since there is no bpf variable in there. Would you mind sharing the whole configuration?

[joelasagne]

Hi, here is my whole configuration :

local sockets = {}

for i=1,6 do
  xsk = newXsk({ifName="eth4", NIC_queue_id=i-1, frameNums=65536, xskMapPath="/sys/fs/bpf/dnsdist/xskmap"})
  table.insert(sockets, xsk)
  addLocal("192.168.93.225:53", {xskSocket=xsk, reusePort=true})
end

newServer({address="192.168.93.220:53",source="192.168.93.212@eth4", xskSockets=sockets, MACAddr='bc:24:11:90:3a:37', checkName="localhost.", checkType="A",pool="pdns"})
newServer({address="192.168.93.221:53",source="192.168.93.212@eth4", xskSockets=sockets, MACAddr='bc:24:11:06:7d:72', checkName="localhost.", checkType="A",pool="pdns"})
newServer({address="192.168.93.222:53",source="192.168.93.212@eth4", xskSockets=sockets, MACAddr='bc:24:11:9a:27:9f', checkName="localhost.", checkType="A",pool="pdns"})

addACL("0.0.0.0/0")
addACL("::/0")
setKey("redacted")
controlSocket("127.0.0.1:5199")
webserver("127.0.0.1:8053")
setWebserverConfig({password="$scrypt$redacted", apiKey="$scrypt$redacted"})

getPool("pdns"):setCache(newPacketCache(
  1000000,
  {
    dontAge=true,
    maxNegativeTTL=600,
    maxTTL=60
  }
))

bpf = newBPFFilter({
    ipv4MaxItems=1048576,
    ipv4PinnedPath="/var/run/dnsdist/v4filter",
    ipv6MaxItems=1048576,
    ipv6PinnedPath="/var/run/dnsdist/v6filter",
    qnamesMaxItems=32,
    qnamesPinnedPath="/var/run/dnsdist/qnamefilter",
    cidr4MaxItems=32,
    cidr4PinnedPath="/var/run/dnsdist/cidr4filter",
    cidr6MaxItems=32,
    cidr6PinnedPath="/var/run/dnsdist/cidr6filter",
    external=true
})

pdnsNMG = newNMG()
pdnsNMG:addMask("192.168.93.225")
addAction(NetmaskGroupRule(pdnsNMG , false),PoolAction("pdns"))