Update man page on XDP configuration

nsd.conf.5.in

@@ -605,17 +605,31 @@ traffic, for UDP, TCP and for TLS service.
 .B xdp\-interface:\fR <string>
 The interface to use XDP with. This enables the use of AF_XDP sockets.
 Default is "", disabled.
+.IP
+.\" Considerations probably need improvement in format and wording
+Considerations:
+.br
+\(bu If \fBcpu-affinity\fR is configured, please be aware of the cpu affinity
+of network device queues.
+.br
+\(bu It is assumed that the interface only uses combined rx/tx channels/queues.
+.br
+\(bu As many processes as there are combined channels on the specified
+interface will receive traffic via XDP. \fBserver-count\fR will be increased if
+necessary. If \fBserver-count\fR is higher, the excess processes will not
+interact with XDP.
 .TP
 .B xdp\-program\-path:\fR <string>
 The eBPF XDP program to extract the XSKMAP from. Specify your own program here,
 if you want to use a custom XDP program. The default program shipped with NSD
 only redirects UDP (over Ethernet[+VLAN]+IPv4/6) traffic to port 53.
 When using your own XDP program, it needs to define a BPF_MAP_TYPE_XSKMAP
 named "xsks_map" and pin it (see \fBxdp-bpffs-path\fR) with read and write
-permission for NSD. This option needs to be set, even when NSD is configured
-not to load the specified XDP program (see \fBxdp-program-load\fR),
-to be able to access the XSKMAP.
-Default is "@sharedfilesdir@/xdp-dns-redirect_kern.o".
+permission for NSD.
+.IP
+This option needs to be set, even when NSD is configured not to load the
+specified XDP program (see \fBxdp-program-load\fR), to be able to determine the
+XSKMAP structure. Default is "@sharedfilesdir@/xdp-dns-redirect_kern.o".
 .TP
 .B xdp\-program\-load:\fR <yes or no>
 Specify whether NSD should load the XDP program. If set to no, you need