controller: fix possible unaligned accesses in DHCPv6 code

According to RFC8415 [0], section 8 "Client/Server Message Formats":
"Options are stored serially in the "options" field, with no padding
 between the options.  Options are byte-aligned but are not aligned
 in any other way (such as on 2-byte or 4-byte boundaries)."

Fix possible unaligned accesses in DHCPv6 code reading/writing
getting rid of dhcp_opt6_header structure that trigger undefined
behaviour issues reported by ubsan sanitizer and relying on
dhcpv6_opt_header that is defined as packed.

[0] https://www.rfc-editor.org/rfc/rfc8415.html

Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Acked-by: Mark Michelson <mmichels@redhat.com>
Signed-off-by: Numan Siddique <numans@ovn.org>
(cherry picked from commit 8298eac)

controller/pinctrl.c

@@ -2368,19 +2368,19 @@ compose_out_dhcpv6_opts(struct ofpbuf *userdata,
                         struct ofpbuf *out_dhcpv6_opts, ovs_be32 iaid)
 {
     while (userdata->size) {
-        struct dhcp_opt6_header *userdata_opt = ofpbuf_try_pull(
+        struct dhcpv6_opt_header *userdata_opt = ofpbuf_try_pull(
             userdata, sizeof *userdata_opt);
         if (!userdata_opt) {
             return false;
         }
 
-        size_t size = ntohs(userdata_opt->size);
+        size_t size = ntohs(userdata_opt->len);
         uint8_t *userdata_opt_data = ofpbuf_try_pull(userdata, size);
         if (!userdata_opt_data) {
             return false;
         }
 
-        switch (ntohs(userdata_opt->opt_code)) {
+        switch (ntohs(userdata_opt->code)) {
         case DHCPV6_OPT_SERVER_ID_CODE:
         {
             /* The Server Identifier option carries a DUID

lib/actions.c

@@ -2875,26 +2875,26 @@ static void
 encode_put_dhcpv6_option(const struct ovnact_gen_option *o,
                          struct ofpbuf *ofpacts)
 {
-    struct dhcp_opt6_header *opt = ofpbuf_put_uninit(ofpacts, sizeof *opt);
+    struct dhcpv6_opt_header *opt = ofpbuf_put_uninit(ofpacts, sizeof *opt);
     const union expr_constant *c = o->value.values;
     size_t n_values = o->value.n_values;
     size_t size;
 
-    opt->opt_code = htons(o->option->code);
+    opt->code = htons(o->option->code);
 
     if (!strcmp(o->option->type, "ipv6")) {
         size = n_values * sizeof(struct in6_addr);
-        opt->size = htons(size);
+        opt->len = htons(size);
         for (size_t i = 0; i < n_values; i++) {
             ofpbuf_put(ofpacts, &c[i].value.ipv6, sizeof(struct in6_addr));
         }
     } else if (!strcmp(o->option->type, "mac")) {
         size = sizeof(struct eth_addr);
-        opt->size = htons(size);
+        opt->len = htons(size);
         ofpbuf_put(ofpacts, &c->value.mac, size);
     } else if (!strcmp(o->option->type, "str")) {
         size = strlen(c->string);
-        opt->size = htons(size);
+        opt->len = htons(size);
         ofpbuf_put(ofpacts, c->string, size);
     }
 }

lib/ovn-l7.h

@@ -228,12 +228,6 @@ struct dhcp_opt_header {
 #define DHCP_OPT_PAYLOAD(hdr) \
     (void *)((char *)hdr + sizeof(struct dhcp_opt_header))
 
-/* Used in the OpenFlow PACKET_IN userdata */
-struct dhcp_opt6_header {
-    ovs_be16 opt_code;
-    ovs_be16 size;
-};
-
 /* These are not defined in ovs/lib/dhcp.h, hence defining here. */
 #define OVN_DHCP_MSG_DECLINE        4
 #define OVN_DHCP_MSG_RELEASE        7