[lib][minip] a few fixes

-Add C++ header guards around the public api.
-Fix a divide by zero bug in the test console routine.
-Add a new pktbuf api to assist with resetting a pktbuf back to default
values for reuse in an ethernet driver.

lib/minip/include/lib/minip.h

@@ -8,6 +8,7 @@
  */
 #pragma once
 
+#include <lk/compiler.h>
 #include <endian.h>
 #include <lk/list.h>
 #include <stdint.h>
@@ -16,6 +17,8 @@
 
 #include <lib/pktbuf.h>
 
+__BEGIN_CDECLS
+
 #define IPV4(a,b,c,d) (((a)&0xFF)|(((b)&0xFF)<<8)|(((c)&0xFF)<<16)|(((d)&0xFF)<<24))
 #define IPV4_SPLIT(a) (a & 0xFF), ((a >> 8) & 0xFF), ((a >> 16) & 0xFF), ((a >> 24) & 0xFF)
 #define IPV4_PACK(a) (a[3] << 24 | a[2] << 16 | a[1] << 8 | a[0])
@@ -72,3 +75,5 @@ static inline status_t tcp_accept(tcp_socket_t *listen_socket, tcp_socket_t **ac
 
 /* utilities */
 void gen_random_mac_address(uint8_t *mac_addr);
+
+__END_CDECLS

lib/minip/include/lib/pktbuf.h

@@ -9,6 +9,9 @@
 
 #include <sys/types.h>
 #include <lk/list.h>
+#include <lk/compiler.h>
+
+__BEGIN_CDECLS
 
 /* PAGE_SIZE minus 16 bytes of metadata in pktbuf_buf */
 #ifndef PKTBUF_POOL_SIZE
@@ -72,6 +75,7 @@ pktbuf_t *pktbuf_alloc_empty(void);
 /* Add a buffer to an existing packet buffer */
 void pktbuf_add_buffer(pktbuf_t *p, u8 *buf, u32 len, uint32_t header_sz,
                        uint32_t flags, pktbuf_free_callback cb, void *cb_args);
+
 // return packet buffer to buffer pool
 // returns number of threads woken up
 int pktbuf_free(pktbuf_t *p, bool reschedule);
@@ -96,6 +100,12 @@ void *pktbuf_consume(pktbuf_t *p, size_t sz);
 // remove sz bytes from the end of the pktbuf
 void pktbuf_consume_tail(pktbuf_t *p, size_t sz);
 
+// reset the header size to header_sz into the underlying buffer.
+// p->dlen is also set to 0.
+// pktbuf must have a buffer with a valid blen and header_sz must
+// be within the buffer.
+void pktbuf_reset(pktbuf_t *p, uint32_t header_sz);
+
 // create a new packet buffer from raw memory and add
 // it to the free pool
 void pktbuf_create(void *ptr, size_t size);
@@ -104,3 +114,5 @@ void pktbuf_create(void *ptr, size_t size);
 void pktbuf_create_bufs(void *ptr, size_t size);
 
 void pktbuf_dump(pktbuf_t *p);
+
+__END_CDECLS

lib/minip/lk_console.c

@@ -117,7 +117,7 @@ minip_usage:
                 memset(buf, 0x00, BUFSIZE);
                 printf("sending %u packet(s) to %u.%u.%u.%u:%u\n", count, IPV4_SPLIT(host), port);
 
-                lk_time_t t = current_time();
+                lk_bigtime_t t = current_time_hires();
                 uint32_t failures = 0;
                 for (uint32_t i = 0; i < count; i++) {
                     if (udp_send(buf, BUFSIZE, handle) != 0) {
@@ -125,11 +125,13 @@ minip_usage:
                     }
                     buf[128]++;
                 }
-                t = current_time() - t;
+                t = current_time_hires() - t;
+                if (t == 0)
+                    t++;
                 printf("%d pkts failed\n", failures);
                 uint64_t total_count = (uint64_t)count * BUFSIZE;
                 printf("wrote %llu bytes in %u msecs (%llu bytes/sec)\n",
-                       total_count, (uint32_t)t, total_count * 1000 / t);
+                       total_count, (uint32_t)t, total_count * 1000000 / t);
 
                 free(buf);
                 udp_close(handle);

lib/minip/pktbuf.c

@@ -117,6 +117,15 @@ pktbuf_t *pktbuf_alloc(void) {
     return p;
 }
 
+void pktbuf_reset(pktbuf_t *p, uint32_t header_sz) {
+    DEBUG_ASSERT(p);
+    DEBUG_ASSERT(p->buffer);
+    DEBUG_ASSERT(header_sz < p->blen);
+
+    p->data = p->buffer + header_sz;
+    p->dlen = 0;
+}
+
 pktbuf_t *pktbuf_alloc_empty(void) {
     pktbuf_t *p = (pktbuf_t *) get_pool_object();