selftests: net: test IPV6_HOPLIMIT

Test setting IPV6_HOPLIMIT via setsockopt and cmsg
across socket types.

Output without the kernel support (this series):

  Case HOPLIMIT ICMP cmsg - packet data returned 1, expected 0
  Case HOPLIMIT ICMP diff - packet data returned 1, expected 0
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/cmsg_ipv6.sh

@@ -106,6 +106,37 @@ for ovr in setsock cmsg both diff; do
     done
 done
 
+# IPV6_HOPLIMIT
+LIM=4
+
+for ovr in setsock cmsg both diff; do
+    for p in u i r; do
+	[ $p == "u" ] && prot=UDP
+	[ $p == "i" ] && prot=ICMP
+	[ $p == "r" ] && prot=RAW
+
+	[ $ovr == "setsock" ] && m="-L"
+	[ $ovr == "cmsg" ]    && m="-l"
+	[ $ovr == "both" ]    && m="-L $LIM -l"
+	[ $ovr == "diff" ]    && m="-L $((LIM + 1)) -l"
+
+	$NSEXE nohup tcpdump --immediate-mode -p -ni dummy0 -w $TMPF -c 4 2> /dev/null &
+	BG=$!
+	sleep 0.05
+
+	$NSEXE ./cmsg_sender -6 -p $p $m $LIM $TGT6 1234
+	check_result $? 0 "HOPLIMIT $prot $ovr - pass"
+
+	while [ -d /proc/$BG ]; do
+	    $NSEXE ./cmsg_sender -6 -p u $TGT6 1234
+	done
+
+	tcpdump -r $TMPF -v 2>&1 | grep "hlim $LIM[^0-9]" >> /dev/null
+	check_result $? 0 "HOPLIMIT $prot $ovr - packet data"
+	rm $TMPF
+    done
+done
+
 # Summary
 if [ $BAD -ne 0 ]; then
     echo "FAIL - $BAD/$TOTAL cases failed"

tools/testing/selftests/net/cmsg_sender.c

@@ -47,6 +47,7 @@ struct options {
 		unsigned int mark;
 		unsigned int dontfrag;
 		unsigned int tclass;
+		unsigned int hlimit;
 	} sockopt;
 	struct {
 		unsigned int family;
@@ -64,6 +65,7 @@ struct options {
 	struct {
 		struct option_cmsg_u32 dontfrag;
 		struct option_cmsg_u32 tclass;
+		struct option_cmsg_u32 hlimit;
 	} v6;
 } opt = {
 	.size = 13,
@@ -95,6 +97,8 @@ static void __attribute__((noreturn)) cs_usage(const char *bin)
 	       "\t\t-F val  Set don't fragment via setsockopt\n"
 	       "\t\t-c val  Set TCLASS via cmsg\n"
 	       "\t\t-C val  Set TCLASS via setsockopt\n"
+	       "\t\t-l val  Set HOPLIMIT via cmsg\n"
+	       "\t\t-L val  Set HOPLIMIT via setsockopt\n"
 	       "");
 	exit(ERN_HELP);
 }
@@ -103,7 +107,7 @@ static void cs_parse_args(int argc, char *argv[])
 {
 	char o;
 
-	while ((o = getopt(argc, argv, "46sS:p:m:M:d:tf:F:c:C:")) != -1) {
+	while ((o = getopt(argc, argv, "46sS:p:m:M:d:tf:F:c:C:l:L:")) != -1) {
 		switch (o) {
 		case 's':
 			opt.silent_send = true;
@@ -158,6 +162,13 @@ static void cs_parse_args(int argc, char *argv[])
 		case 'C':
 			opt.sockopt.tclass = atoi(optarg);
 			break;
+		case 'l':
+			opt.v6.hlimit.ena = true;
+			opt.v6.hlimit.val = atoi(optarg);
+			break;
+		case 'L':
+			opt.sockopt.hlimit = atoi(optarg);
+			break;
 		}
 	}
 
@@ -215,6 +226,8 @@ cs_write_cmsg(int fd, struct msghdr *msg, char *cbuf, size_t cbuf_sz)
 			  SOL_IPV6, IPV6_DONTFRAG, &opt.v6.dontfrag);
 	ca_write_cmsg_u32(cbuf, cbuf_sz, &cmsg_len,
 			  SOL_IPV6, IPV6_TCLASS, &opt.v6.tclass);
+	ca_write_cmsg_u32(cbuf, cbuf_sz, &cmsg_len,
+			  SOL_IPV6, IPV6_HOPLIMIT, &opt.v6.hlimit);
 
 	if (opt.txtime.ena) {
 		struct sock_txtime so_txtime = {
@@ -360,6 +373,10 @@ static void ca_set_sockopts(int fd)
 	    setsockopt(fd, SOL_IPV6, IPV6_TCLASS,
 		       &opt.sockopt.tclass, sizeof(opt.sockopt.tclass)))
 		error(ERN_SOCKOPT, errno, "setsockopt IPV6_TCLASS");
+	if (opt.sockopt.hlimit &&
+	    setsockopt(fd, SOL_IPV6, IPV6_UNICAST_HOPS,
+		       &opt.sockopt.hlimit, sizeof(opt.sockopt.hlimit)))
+		error(ERN_SOCKOPT, errno, "setsockopt IPV6_HOPLIMIT");
 }
 
 int main(int argc, char *argv[])