crda: add regulatory domain optimizer

This adds a regulatory domain optimizer which can be
used with information of a regulatory domain in db.txt
format in stdin. It makes use of the new shiny regulatory
domain stream parser.

The way this works is it iterates over the regulatory domain
computing unions between each frequency, starting from each
frequency as a pivot. If a union leads to a valid regulatory
rule we verify that the pivot and othre frequency rules that
provided that valid union can fit into that union regulatory
rule by computing an intersection. If an intersection is
possible it means two rules can be optimized out. We do
this repetitively.

Note: cfg80211's nl80211.h API has:

      #define NL80211_MAX_SUPP_REG_RULES              32

Our tools, both the stream parser and the optimizer are not
limited to these artificial limits ! We can work on extending
the kernel's limit but so far we have had no needs. A few
notes below though on the existing reasoning for the limit
and possible future enhancements.

This is used nl80211_set_reg() upon intercept of a regulatory
domain being sent from userspace to it. We picked a limitation
to at least have a stopping gap to avoid userpace flooding the
kernel with a denial of service requests on memory from userspace.
This means that userspace can only request at most a kmalloc
of up to 32 regulatory rules for processing for the regulatory
data that we are copying from userspace. There's a Linux kernel
enhancement that will be made soon so that we invalidate bogus
requests, by checking to see if the incomming regulatory domain
alpha2 was not expected upon a regulatory hint initiator (even
if userspace first tells the kernel it is waiting for a response
from kernel space), and if its invalid then we drop the userspace
supplied request, therefore avoiding some form of flooding on
memory to the kernel.

Note that we can still get flooding if the userspace API is used
to *request* to the kernel for a regulatory domain to be sent
from userspace, in that case the kernel will properly expect the
regulatory data for the alpha2. To prevent flooding there perhaps
its a good idea for us to check whether a userspace pending request
is pendingg and if so deny new updates until the last one triggers
a timeout.

Screenshot for a US file with 40 rules:

mcgrof@frijol ~/devel/xlreg (git::master)$ cat us | grep --"(" | wc -l
40

mcgrof@frijol ~/devel/crda (git::master)$ cat us
country US: DFS-FCC
        (2402.000 - 2422.000 @ 20.000), (30.00)
        (2407.000 - 2427.000 @ 20.000), (30.00)
        (2412.000 - 2432.000 @ 20.000), (30.00)
        (2417.000 - 2437.000 @ 20.000), (30.00)
        (2422.000 - 2442.000 @ 20.000), (30.00)
        (2427.000 - 2447.000 @ 20.000), (30.00)
        (2432.000 - 2452.000 @ 20.000), (30.00)
        (2437.000 - 2457.000 @ 20.000), (30.00)
        (2442.000 - 2462.000 @ 20.000), (30.00)
        (2447.000 - 2467.000 @ 20.000), (30.00)
        (2452.000 - 2472.000 @ 20.000), (30.00)
        (2402.000 - 2442.000 @ 40.000), (30.00)
        (2407.000 - 2447.000 @ 40.000), (30.00)
        (2412.000 - 2452.000 @ 40.000), (30.00)
        (2417.000 - 2457.000 @ 40.000), (30.00)
        (2422.000 - 2462.000 @ 40.000), (30.00)
        (2427.000 - 2467.000 @ 40.000), (30.00)
        (2432.000 - 2472.000 @ 40.000), (30.00)
        (5170.000 - 5190.000 @ 20.000), (17.00)
        (5190.000 - 5210.000 @ 20.000), (17.00)
        (5210.000 - 5230.000 @ 20.000), (17.00)
        (5230.000 - 5250.000 @ 20.000), (17.00)
        (5250.000 - 5270.000 @ 20.000), (23.00), DFS
        (5270.000 - 5290.000 @ 20.000), (23.00), DFS
        (5290.000 - 5310.000 @ 20.000), (23.00), DFS
        (5310.000 - 5330.000 @ 20.000), (23.00), DFS
        (5735.000 - 5755.000 @ 20.000), (30.00)
        (5755.000 - 5775.000 @ 20.000), (30.00)
        (5775.000 - 5795.000 @ 20.000), (30.00)
        (5795.000 - 5815.000 @ 20.000), (30.00)
        (5815.000 - 5835.000 @ 20.000), (30.00)
        (5170.000 - 5210.000 @ 40.000), (17.00)
        (5210.000 - 5250.000 @ 40.000), (17.00)
        (5250.000 - 5290.000 @ 40.000), (23.00), DFS
        (5290.000 - 5330.000 @ 40.000), (23.00), DFS
        (5735.000 - 5775.000 @ 40.000), (30.00)
        (5775.000 - 5815.000 @ 40.000), (30.00)
        (5170.000 - 5250.000 @ 80.000), (17.00)
        (5250.000 - 5330.000 @ 80.000), (23.00), DFS
        (5735.000 - 5815.000 @ 80.000), (30.00)

mcgrof@frijol ~/devel/crda (git::master)$ cat us | ./optimize
country US: DFS-FCC
        (2402.000 - 2472.000 @ 40.000), (30.00)
        (5170.000 - 5250.000 @ 80.000), (17.00)
        (5250.000 - 5330.000 @ 80.000), (23.00), DFS
        (5735.000 - 5835.000 @ 80.000), (30.00)

I've also tested this with the current db.txt from wireless-regdb
and get real optimiziations which I will post later.

Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>

Author: mcgrof

Makefile

@@ -28,7 +28,7 @@ LDLIBS += -lm
 
 all: all_noverify verify
 
-all_noverify: crda intersect regdbdump db2rd
+all_noverify: crda intersect regdbdump db2rd optimize
 
 ifeq ($(USE_OPENSSL),1)
 CFLAGS += -DUSE_OPENSSL -DPUBKEY_DIR=\"$(RUNTIME_PUBKEY_DIR)\" `pkg-config --cflags openssl`
@@ -126,6 +126,10 @@ db2rd: reglib.o db2rd.o
 	$(NQ) '  LD  ' $@
 	$(Q)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ $(LDLIBS)
 
+optimize: reglib.o optimize.o
+	$(NQ) '  LD  ' $@
+	$(Q)$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $^ $(LDLIBS)
+
 verify: $(REG_BIN) regdbdump
 	$(NQ) '  CHK  $(REG_BIN)'
 	$(Q)./regdbdump $(REG_BIN) >/dev/null
@@ -157,6 +161,6 @@ install: crda crda.8.gz regdbdump.8.gz
 	$(Q)$(INSTALL) -m 644 -t $(DESTDIR)/$(MANDIR)/man8/ regdbdump.8.gz
 
 clean:
-	$(Q)rm -f crda regdbdump intersect db2rd \
+	$(Q)rm -f crda regdbdump intersect db2rd optimize \
 		*.o *~ *.pyc keys-*.c *.gz \
 	udev/$(UDEV_LEVEL)regulatory.rules udev/regulatory.rules.parsed

optimize.c

@@ -0,0 +1,40 @@
+#include <errno.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <arpa/inet.h> /* ntohl */
+#include <string.h>
+
+#include "nl80211.h"
+#include "reglib.h"
+
+int main(int argc, char **argv)
+{
+	struct ieee80211_regdomain *rd = NULL, *rd_opt = NULL;
+	FILE *fp;
+
+	if (argc != 1) {
+		fprintf(stderr, "Usage: cat db.txt | %s\n", argv[0]);
+		return -EINVAL;
+	}
+
+	fp = reglib_create_parse_stream(stdin);
+	if (!fp)
+		return -EINVAL;
+
+	reglib_for_each_country_stream(fp, rd) {
+		rd_opt = reglib_optimize_regdom(rd);
+		if (!rd_opt){
+			fprintf(stderr, "Unable to optimize %c%c\n",
+				rd->alpha2[0],
+				rd->alpha2[1]);
+			free(rd);
+			continue;
+		}
+		reglib_print_regdom(rd_opt);
+		free(rd);
+		free(rd_opt);
+	}
+
+	fclose(fp);
+	return 0;
+}