Merge pull request #20984 from benpicco/gnrc_pktsnip_t-shrink

sys/net/gnrc/pkt: use `uint8_t` for user count

sys/include/net/gnrc/pkt.h

@@ -110,17 +110,18 @@ typedef struct gnrc_pktsnip {
     struct gnrc_pktsnip *next;      /**< next snip in the packet */
     void *data;                     /**< pointer to the data of the snip */
     size_t size;                    /**< the length of the snip in byte */
+    /* end of iolist_t */
+#ifdef MODULE_GNRC_NETERR
+    kernel_pid_t err_sub;           /**< subscriber to errors related to this
+                                     *   packet snip */
+#endif
+    gnrc_nettype_t type;            /**< protocol of the packet snip */
     /**
      * @brief   Counter of threads currently having control over this packet.
      *
      * @internal
      */
-    unsigned int users;
-    gnrc_nettype_t type;            /**< protocol of the packet snip */
-#ifdef MODULE_GNRC_NETERR
-    kernel_pid_t err_sub;           /**< subscriber to errors related to this
-                                     *   packet snip */
-#endif
+    uint8_t users;
 } gnrc_pktsnip_t;
 
 /**

sys/net/gnrc/netapi/gnrc_netapi.c

@@ -92,6 +92,7 @@ int gnrc_netapi_dispatch(gnrc_nettype_t type, uint32_t demux_ctx,
     if (numof != 0) {
         gnrc_netreg_entry_t *sendto = gnrc_netreg_lookup(type, demux_ctx);
 
+        /* the packet is replicated over all interfaces that is's being sent on */
         gnrc_pktbuf_hold(pkt, numof - 1);
 
         while (sendto) {

sys/net/gnrc/network_layer/ipv6/gnrc_ipv6.c

@@ -576,7 +576,7 @@ static void _send_multicast(gnrc_pktsnip_t *pkt, bool prep_hdr,
     if (!gnrc_netif_highlander()) {
         /* interface not given: send over all interfaces */
         if (netif == NULL) {
-            /* send packet to link layer */
+            /* the packet is replicated over all interfaces that is's being sent on */
             gnrc_pktbuf_hold(pkt, ifnum - 1);
 
             while ((netif = gnrc_netif_iter(netif))) {

sys/net/gnrc/pktbuf_malloc/gnrc_pktbuf_malloc.c

@@ -210,6 +210,7 @@ void gnrc_pktbuf_hold(gnrc_pktsnip_t *pkt, unsigned int num)
 {
     mutex_lock(&gnrc_pktbuf_mutex);
     while (pkt) {
+        assert(pkt->users + num <= 0xff);
         pkt->users += num;
         pkt = pkt->next;
     }

sys/net/gnrc/pktbuf_static/gnrc_pktbuf_static.c

@@ -213,6 +213,7 @@ void gnrc_pktbuf_hold(gnrc_pktsnip_t *pkt, unsigned int num)
 {
     mutex_lock(&gnrc_pktbuf_mutex);
     while (pkt) {
+        assert(pkt->users + num <= 0xff);
         pkt->users += num;
         pkt = pkt->next;
     }

tests/unittests/tests-pktbuf/tests-pktbuf.c

@@ -325,7 +325,10 @@ static void test_pktbuf_mark__pkt_NOT_NULL__size_greater_than_pkt_size(void)
 
 static void test_pktbuf_mark__pkt_NOT_NULL__pkt_data_NULL(void)
 {
-    gnrc_pktsnip_t pkt = { NULL, NULL, sizeof(TEST_STRING16), 1, GNRC_NETTYPE_TEST };
+    gnrc_pktsnip_t pkt = { .size  = sizeof(TEST_STRING16),
+                           .type  = GNRC_NETTYPE_TEST,
+                           .users = 1,
+                         };
 
     TEST_ASSERT_NULL(gnrc_pktbuf_mark(&pkt, sizeof(TEST_STRING16) - 1,
                                       GNRC_NETTYPE_TEST));

tests/unittests/tests-pktqueue/tests-pktqueue.c

@@ -21,8 +21,8 @@
 #include "unittests-constants.h"
 #include "tests-pktqueue.h"
 
-#define PKT_INIT_ELEM(len, data, next) \
-    { (next), (void *)(data), (len), 1, GNRC_NETTYPE_UNDEF }
+#define PKT_INIT_ELEM(len, ptr, nxt) \
+    { .next = (nxt), .data = (void *)(ptr), .size = (len), .users = 1, .type = GNRC_NETTYPE_UNDEF }
 #define PKT_INIT_ELEM_STATIC_DATA(data, next) PKT_INIT_ELEM(sizeof(data), (void *)(data), (next))
 #define PKTQUEUE_INIT_ELEM(pkt) { NULL, pkt }
 

tests/unittests/tests-priority_pktqueue/tests-priority_pktqueue.c

@@ -22,8 +22,8 @@
 #include "unittests-constants.h"
 #include "tests-priority_pktqueue.h"
 
-#define PKT_INIT_ELEM(len, data, next) \
-    { (next), (void *)(data), (len), 1, GNRC_NETTYPE_UNDEF }
+#define PKT_INIT_ELEM(len, ptr, nxt) \
+    { .next = (nxt), .data = (void *)(ptr), .size = (len), .users = 1, .type = GNRC_NETTYPE_UNDEF }
 #define PKT_INIT_ELEM_STATIC_DATA(data, next) PKT_INIT_ELEM(sizeof(data), (void *)(data), (next))
 #define PKTQUEUE_INIT_ELEM(pkt) { NULL, pkt }