X-Git-Url: http://git.onelab.eu/?a=blobdiff_plain;f=lib%2Fofpbuf.c;h=1f4b61dc01f92076a4b838b0ffcb6a504f129e42;hb=0ef165ecb57943e17a8ee8270df68ffb8d032e29;hp=9cb2ceb80f7adc0d03b906d3b6552a78a65138d3;hpb=a0bc29a541fc7dc6e20137d5558e2094d614e6ab;p=sliver-openvswitch.git

diff --git a/lib/ofpbuf.c b/lib/ofpbuf.c
index 9cb2ceb80..1f4b61dc0 100644
--- a/lib/ofpbuf.c
+++ b/lib/ofpbuf.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,28 +16,107 @@
 
 #include <config.h>
 #include "ofpbuf.h"
-#include <assert.h>
 #include <stdlib.h>
 #include <string.h>
 #include "dynamic-string.h"
+#include "netdev-dpdk.h"
 #include "util.h"
 
+static void
+ofpbuf_init__(struct ofpbuf *b, size_t allocated, enum ofpbuf_source source)
+{
+    b->allocated = allocated;
+    b->source = source;
+    b->frame = NULL;
+    b->l2_5_ofs = b->l3_ofs = b->l4_ofs = UINT16_MAX;
+    list_poison(&b->list_node);
+}
+
+static void
+ofpbuf_use__(struct ofpbuf *b, void *base, size_t allocated,
+             enum ofpbuf_source source)
+{
+    ofpbuf_set_base(b, base);
+    ofpbuf_set_data(b, base);
+    ofpbuf_set_size(b, 0);
+
+    ofpbuf_init__(b, allocated, source);
+}
+
 /* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
- * memory starting at 'base'.
- *
- * 'base' should ordinarily be the first byte of a region obtained from
- * malloc(), but in circumstances where it can be guaranteed that 'b' will
- * never need to be expanded or freed, it can be a pointer into arbitrary
- * memory. */
+ * memory starting at 'base'.  'base' should be the first byte of a region
+ * obtained from malloc().  It will be freed (with free()) if 'b' is resized or
+ * freed. */
 void
 ofpbuf_use(struct ofpbuf *b, void *base, size_t allocated)
 {
-    b->base = b->data = base;
-    b->allocated = allocated;
-    b->size = 0;
-    b->l2 = b->l3 = b->l4 = b->l7 = NULL;
-    b->next = NULL;
-    b->private_p = NULL;
+    ofpbuf_use__(b, base, allocated, OFPBUF_MALLOC);
+}
+
+/* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
+ * memory starting at 'base'.  'base' should point to a buffer on the stack.
+ * (Nothing actually relies on 'base' being allocated on the stack.  It could
+ * be static or malloc()'d memory.  But stack space is the most common use
+ * case.)
+ *
+ * 'base' should be appropriately aligned.  Using an array of uint32_t or
+ * uint64_t for the buffer is a reasonable way to ensure appropriate alignment
+ * for 32- or 64-bit data.
+ *
+ * An ofpbuf operation that requires reallocating data will assert-fail if this
+ * function was used to initialize it.  Thus, one need not call ofpbuf_uninit()
+ * on an ofpbuf initialized by this function (though doing so is harmless),
+ * because it is guaranteed that 'b' does not own any heap-allocated memory. */
+void
+ofpbuf_use_stack(struct ofpbuf *b, void *base, size_t allocated)
+{
+    ofpbuf_use__(b, base, allocated, OFPBUF_STACK);
+}
+
+/* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
+ * memory starting at 'base'.  'base' should point to a buffer on the stack.
+ * (Nothing actually relies on 'base' being allocated on the stack.  It could
+ * be static or malloc()'d memory.  But stack space is the most common use
+ * case.)
+ *
+ * 'base' should be appropriately aligned.  Using an array of uint32_t or
+ * uint64_t for the buffer is a reasonable way to ensure appropriate alignment
+ * for 32- or 64-bit data.
+ *
+ * An ofpbuf operation that requires reallocating data will copy the provided
+ * buffer into a malloc()'d buffer.  Thus, it is wise to call ofpbuf_uninit()
+ * on an ofpbuf initialized by this function, so that if it expanded into the
+ * heap, that memory is freed. */
+void
+ofpbuf_use_stub(struct ofpbuf *b, void *base, size_t allocated)
+{
+    ofpbuf_use__(b, base, allocated, OFPBUF_STUB);
+}
+
+/* Initializes 'b' as an ofpbuf whose data starts at 'data' and continues for
+ * 'size' bytes.  This is appropriate for an ofpbuf that will be used to
+ * inspect existing data, without moving it around or reallocating it, and
+ * generally without modifying it at all.
+ *
+ * An ofpbuf operation that requires reallocating data will assert-fail if this
+ * function was used to initialize it. */
+void
+ofpbuf_use_const(struct ofpbuf *b, const void *data, size_t size)
+{
+    ofpbuf_use__(b, CONST_CAST(void *, data), size, OFPBUF_STACK);
+    ofpbuf_set_size(b, size);
+}
+
+/* Initializes 'b' as an empty ofpbuf that contains the 'allocated' bytes of
+ * memory starting at 'base'.  DPDK allocated ofpbuf and *data is allocated
+ * from one continous memory region, so in memory data start right after
+ * ofpbuf.  Therefore there is special method to free this type of
+ * buffer.  ofpbuf base, data and size are initialized by dpdk rcv() so no
+ * need to initialize those fields. */
+void
+ofpbuf_init_dpdk(struct ofpbuf *b, size_t allocated)
+{
+    ofpbuf_init__(b, allocated, OFPBUF_DPDK);
 }
 
 /* Initializes 'b' as an empty ofpbuf with an initial capacity of 'size'
@@ -50,10 +129,13 @@ ofpbuf_init(struct ofpbuf *b, size_t size)
 
 /* Frees memory that 'b' points to. */
 void
-ofpbuf_uninit(struct ofpbuf *b) 
+ofpbuf_uninit(struct ofpbuf *b)
 {
     if (b) {
-        free(b->base);
+        if (b->source == OFPBUF_MALLOC) {
+            free(ofpbuf_base(b));
+        }
+        ovs_assert(b->source != OFPBUF_DPDK);
     }
 }
 
@@ -75,93 +157,196 @@ ofpbuf_new(size_t size)
     return b;
 }
 
+/* Creates and returns a new ofpbuf with an initial capacity of 'size +
+ * headroom' bytes, reserving the first 'headroom' bytes as headroom. */
+struct ofpbuf *
+ofpbuf_new_with_headroom(size_t size, size_t headroom)
+{
+    struct ofpbuf *b = ofpbuf_new(size + headroom);
+    ofpbuf_reserve(b, headroom);
+    return b;
+}
+
+/* Creates and returns a new ofpbuf that initially contains a copy of the
+ * 'ofpbuf_size(buffer)' bytes of data starting at 'buffer->data' with no headroom or
+ * tailroom. */
 struct ofpbuf *
 ofpbuf_clone(const struct ofpbuf *buffer)
 {
-    return ofpbuf_clone_data(buffer->data, buffer->size);
+    return ofpbuf_clone_with_headroom(buffer, 0);
+}
+
+/* Creates and returns a new ofpbuf whose data are copied from 'buffer'.   The
+ * returned ofpbuf will additionally have 'headroom' bytes of headroom. */
+struct ofpbuf *
+ofpbuf_clone_with_headroom(const struct ofpbuf *buffer, size_t headroom)
+{
+    struct ofpbuf *new_buffer;
+
+    new_buffer = ofpbuf_clone_data_with_headroom(ofpbuf_data(buffer),
+                                                 ofpbuf_size(buffer),
+                                                 headroom);
+    if (buffer->frame) {
+        uintptr_t data_delta
+            = (char *)ofpbuf_data(new_buffer) - (char *)ofpbuf_data(buffer);
+
+        new_buffer->frame = (char *) buffer->frame + data_delta;
+    }
+    new_buffer->l2_5_ofs = buffer->l2_5_ofs;
+    new_buffer->l3_ofs = buffer->l3_ofs;
+    new_buffer->l4_ofs = buffer->l4_ofs;
+
+    return new_buffer;
 }
 
+/* Creates and returns a new ofpbuf that initially contains a copy of the
+ * 'size' bytes of data starting at 'data' with no headroom or tailroom. */
 struct ofpbuf *
 ofpbuf_clone_data(const void *data, size_t size)
 {
-    struct ofpbuf *b = ofpbuf_new(size);
-    ofpbuf_put(b, data, size);
-    return b;
+    return ofpbuf_clone_data_with_headroom(data, size, 0);
 }
 
-/* Frees memory that 'b' points to, as well as 'b' itself. */
-void
-ofpbuf_delete(struct ofpbuf *b) 
+/* Creates and returns a new ofpbuf that initially contains 'headroom' bytes of
+ * headroom followed by a copy of the 'size' bytes of data starting at
+ * 'data'. */
+struct ofpbuf *
+ofpbuf_clone_data_with_headroom(const void *data, size_t size, size_t headroom)
 {
-    if (b) {
-        ofpbuf_uninit(b);
-        free(b);
-    }
+    struct ofpbuf *b = ofpbuf_new_with_headroom(size, headroom);
+    ofpbuf_put(b, data, size);
+    return b;
 }
 
-/* Returns the number of bytes of headroom in 'b', that is, the number of bytes
- * of unused space in ofpbuf 'b' before the data that is in use.  (Most
- * commonly, the data in a ofpbuf is at its beginning, and thus the ofpbuf's
- * headroom is 0.) */
-size_t
-ofpbuf_headroom(const struct ofpbuf *b)
+static void
+ofpbuf_copy__(struct ofpbuf *b, uint8_t *new_base,
+              size_t new_headroom, size_t new_tailroom)
 {
-    return (char*)b->data - (char*)b->base;
+    const uint8_t *old_base = ofpbuf_base(b);
+    size_t old_headroom = ofpbuf_headroom(b);
+    size_t old_tailroom = ofpbuf_tailroom(b);
+    size_t copy_headroom = MIN(old_headroom, new_headroom);
+    size_t copy_tailroom = MIN(old_tailroom, new_tailroom);
+
+    memcpy(&new_base[new_headroom - copy_headroom],
+           &old_base[old_headroom - copy_headroom],
+           copy_headroom + ofpbuf_size(b) + copy_tailroom);
 }
 
-/* Returns the number of bytes that may be appended to the tail end of ofpbuf
- * 'b' before the ofpbuf must be reallocated. */
-size_t
-ofpbuf_tailroom(const struct ofpbuf *b)
+/* Reallocates 'b' so that it has exactly 'new_headroom' and 'new_tailroom'
+ * bytes of headroom and tailroom, respectively. */
+static void
+ofpbuf_resize__(struct ofpbuf *b, size_t new_headroom, size_t new_tailroom)
 {
-    return (char*)ofpbuf_end(b) - (char*)ofpbuf_tail(b);
+    void *new_base, *new_data;
+    size_t new_allocated;
+
+    new_allocated = new_headroom + ofpbuf_size(b) + new_tailroom;
+
+    switch (b->source) {
+    case OFPBUF_DPDK:
+        OVS_NOT_REACHED();
+
+    case OFPBUF_MALLOC:
+        if (new_headroom == ofpbuf_headroom(b)) {
+            new_base = xrealloc(ofpbuf_base(b), new_allocated);
+        } else {
+            new_base = xmalloc(new_allocated);
+            ofpbuf_copy__(b, new_base, new_headroom, new_tailroom);
+            free(ofpbuf_base(b));
+        }
+        break;
+
+    case OFPBUF_STACK:
+        OVS_NOT_REACHED();
+
+    case OFPBUF_STUB:
+        b->source = OFPBUF_MALLOC;
+        new_base = xmalloc(new_allocated);
+        ofpbuf_copy__(b, new_base, new_headroom, new_tailroom);
+        break;
+
+    default:
+        OVS_NOT_REACHED();
+    }
+
+    b->allocated = new_allocated;
+    ofpbuf_set_base(b, new_base);
+
+    new_data = (char *) new_base + new_headroom;
+    if (ofpbuf_data(b) != new_data) {
+        if (b->frame) {
+            uintptr_t data_delta = (char *) new_data - (char *) ofpbuf_data(b);
+
+            b->frame = (char *) b->frame + data_delta;
+        }
+        ofpbuf_set_data(b, new_data);
+    }
 }
 
 /* Ensures that 'b' has room for at least 'size' bytes at its tail end,
- * reallocating and copying its data if necessary. */
+ * reallocating and copying its data if necessary.  Its headroom, if any, is
+ * preserved. */
 void
-ofpbuf_prealloc_tailroom(struct ofpbuf *b, size_t size) 
+ofpbuf_prealloc_tailroom(struct ofpbuf *b, size_t size)
 {
     if (size > ofpbuf_tailroom(b)) {
-        size_t new_allocated = b->allocated + MAX(size, 64);
-        void *new_base = xmalloc(new_allocated);
-        uintptr_t base_delta = (char*)new_base - (char*)b->base;
-        memcpy(new_base, b->base, b->allocated);
-        free(b->base);
-        b->base = new_base;
-        b->allocated = new_allocated;
-        b->data = (char*)b->data + base_delta;
-        if (b->l2) {
-            b->l2 = (char*)b->l2 + base_delta;
-        }
-        if (b->l3) {
-            b->l3 = (char*)b->l3 + base_delta;
-        }
-        if (b->l4) {
-            b->l4 = (char*)b->l4 + base_delta;
-        }
-        if (b->l7) {
-            b->l7 = (char*)b->l7 + base_delta;
-        }
+        ofpbuf_resize__(b, ofpbuf_headroom(b), MAX(size, 64));
     }
 }
 
+/* Ensures that 'b' has room for at least 'size' bytes at its head,
+ * reallocating and copying its data if necessary.  Its tailroom, if any, is
+ * preserved. */
 void
-ofpbuf_prealloc_headroom(struct ofpbuf *b, size_t size) 
+ofpbuf_prealloc_headroom(struct ofpbuf *b, size_t size)
 {
-    assert(size <= ofpbuf_headroom(b));
+    if (size > ofpbuf_headroom(b)) {
+        ofpbuf_resize__(b, MAX(size, 64), ofpbuf_tailroom(b));
+    }
 }
 
-/* Trims the size of 'b' to fit its actual content. */
+/* Trims the size of 'b' to fit its actual content, reducing its tailroom to
+ * 0.  Its headroom, if any, is preserved.
+ *
+ * Buffers not obtained from malloc() are not resized, since that wouldn't save
+ * any memory. */
 void
 ofpbuf_trim(struct ofpbuf *b)
 {
-    /* XXX These could be supported, but the current client doesn't care. */
-    assert(b->data == b->base);
-    assert(b->l2 == NULL && b->l3 == NULL && b->l4 == NULL && b->l7 == NULL);
-    if (b->allocated > b->size) {
-        b->base = b->data = xrealloc(b->base, b->size);
-        b->allocated = b->size;
+    ovs_assert(b->source != OFPBUF_DPDK);
+
+    if (b->source == OFPBUF_MALLOC
+        && (ofpbuf_headroom(b) || ofpbuf_tailroom(b))) {
+        ofpbuf_resize__(b, 0, 0);
+    }
+}
+
+/* If 'b' is shorter than 'length' bytes, pads its tail out with zeros to that
+ * length. */
+void
+ofpbuf_padto(struct ofpbuf *b, size_t length)
+{
+    if (ofpbuf_size(b) < length) {
+        ofpbuf_put_zeros(b, length - ofpbuf_size(b));
+    }
+}
+
+/* Shifts all of the data within the allocated space in 'b' by 'delta' bytes.
+ * For example, a 'delta' of 1 would cause each byte of data to move one byte
+ * forward (from address 'p' to 'p+1'), and a 'delta' of -1 would cause each
+ * byte to move one byte backward (from 'p' to 'p-1'). */
+void
+ofpbuf_shift(struct ofpbuf *b, int delta)
+{
+    ovs_assert(delta > 0 ? delta <= ofpbuf_tailroom(b)
+               : delta < 0 ? -delta <= ofpbuf_headroom(b)
+               : true);
+
+    if (delta != 0) {
+        char *dst = (char *) ofpbuf_data(b) + delta;
+        memmove(dst, ofpbuf_data(b), ofpbuf_size(b));
+        ofpbuf_set_data(b, dst);
     }
 }
 
@@ -169,12 +354,12 @@ ofpbuf_trim(struct ofpbuf *b)
  * copying its data if necessary.  Returns a pointer to the first byte of the
  * new data, which is left uninitialized. */
 void *
-ofpbuf_put_uninit(struct ofpbuf *b, size_t size) 
+ofpbuf_put_uninit(struct ofpbuf *b, size_t size)
 {
     void *p;
     ofpbuf_prealloc_tailroom(b, size);
     p = ofpbuf_tail(b);
-    b->size += size;
+    ofpbuf_set_size(b, ofpbuf_size(b) + size);
     return p;
 }
 
@@ -193,112 +378,180 @@ ofpbuf_put_zeros(struct ofpbuf *b, size_t size)
  * is reallocated and copied if necessary.  Returns a pointer to the first
  * byte of the data's location in the ofpbuf. */
 void *
-ofpbuf_put(struct ofpbuf *b, const void *p, size_t size) 
+ofpbuf_put(struct ofpbuf *b, const void *p, size_t size)
 {
     void *dst = ofpbuf_put_uninit(b, size);
     memcpy(dst, p, size);
     return dst;
 }
 
+/* Parses as many pairs of hex digits as possible (possibly separated by
+ * spaces) from the beginning of 's', appending bytes for their values to 'b'.
+ * Returns the first character of 's' that is not the first of a pair of hex
+ * digits.  If 'n' is nonnull, stores the number of bytes added to 'b' in
+ * '*n'. */
+char *
+ofpbuf_put_hex(struct ofpbuf *b, const char *s, size_t *n)
+{
+    size_t initial_size = ofpbuf_size(b);
+    for (;;) {
+        uint8_t byte;
+        bool ok;
+
+        s += strspn(s, " \t\r\n");
+        byte = hexits_value(s, 2, &ok);
+        if (!ok) {
+            if (n) {
+                *n = ofpbuf_size(b) - initial_size;
+            }
+            return CONST_CAST(char *, s);
+        }
+
+        ofpbuf_put(b, &byte, 1);
+        s += 2;
+    }
+}
+
 /* Reserves 'size' bytes of headroom so that they can be later allocated with
  * ofpbuf_push_uninit() without reallocating the ofpbuf. */
 void
-ofpbuf_reserve(struct ofpbuf *b, size_t size) 
+ofpbuf_reserve(struct ofpbuf *b, size_t size)
 {
-    assert(!b->size);
+    ovs_assert(!ofpbuf_size(b));
     ofpbuf_prealloc_tailroom(b, size);
-    b->data = (char*)b->data + size;
+    ofpbuf_set_data(b, (char*)ofpbuf_data(b) + size);
+}
+
+/* Reserves 'size' bytes of headroom so that they can be later allocated with
+ * ofpbuf_push_uninit() without reallocating the ofpbuf. */
+void
+ofpbuf_reserve_with_tailroom(struct ofpbuf *b, size_t headroom,
+                             size_t tailroom)
+{
+    ovs_assert(!ofpbuf_size(b));
+    ofpbuf_prealloc_tailroom(b, headroom + tailroom);
+    ofpbuf_set_data(b, (char*)ofpbuf_data(b) + headroom);
 }
 
+/* Prefixes 'size' bytes to the head end of 'b', reallocating and copying its
+ * data if necessary.  Returns a pointer to the first byte of the data's
+ * location in the ofpbuf.  The new data is left uninitialized. */
 void *
-ofpbuf_push_uninit(struct ofpbuf *b, size_t size) 
+ofpbuf_push_uninit(struct ofpbuf *b, size_t size)
 {
     ofpbuf_prealloc_headroom(b, size);
-    b->data = (char*)b->data - size;
-    b->size += size;
-    return b->data;
+    ofpbuf_set_data(b, (char*)ofpbuf_data(b) - size);
+    ofpbuf_set_size(b, ofpbuf_size(b) + size);
+    return ofpbuf_data(b);
 }
 
+/* Prefixes 'size' zeroed bytes to the head end of 'b', reallocating and
+ * copying its data if necessary.  Returns a pointer to the first byte of the
+ * data's location in the ofpbuf. */
 void *
-ofpbuf_push(struct ofpbuf *b, const void *p, size_t size) 
+ofpbuf_push_zeros(struct ofpbuf *b, size_t size)
 {
     void *dst = ofpbuf_push_uninit(b, size);
-    memcpy(dst, p, size);
+    memset(dst, 0, size);
     return dst;
 }
 
-/* If 'b' contains at least 'offset + size' bytes of data, returns a pointer to
- * byte 'offset'.  Otherwise, returns a null pointer. */
+/* Copies the 'size' bytes starting at 'p' to the head end of 'b', reallocating
+ * and copying its data if necessary.  Returns a pointer to the first byte of
+ * the data's location in the ofpbuf. */
 void *
-ofpbuf_at(const struct ofpbuf *b, size_t offset, size_t size) 
+ofpbuf_push(struct ofpbuf *b, const void *p, size_t size)
 {
-    return offset + size <= b->size ? (char *) b->data + offset : NULL;
+    void *dst = ofpbuf_push_uninit(b, size);
+    memcpy(dst, p, size);
+    return dst;
 }
 
-/* Returns a pointer to byte 'offset' in 'b', which must contain at least
- * 'offset + size' bytes of data. */
+/* Returns the data in 'b' as a block of malloc()'d memory and frees the buffer
+ * within 'b'.  (If 'b' itself was dynamically allocated, e.g. with
+ * ofpbuf_new(), then it should still be freed with, e.g., ofpbuf_delete().) */
 void *
-ofpbuf_at_assert(const struct ofpbuf *b, size_t offset, size_t size) 
+ofpbuf_steal_data(struct ofpbuf *b)
 {
-    assert(offset + size <= b->size);
-    return ((char *) b->data) + offset;
-}
+    void *p;
+    ovs_assert(b->source != OFPBUF_DPDK);
 
-/* Returns the byte following the last byte of data in use in 'b'. */
-void *
-ofpbuf_tail(const struct ofpbuf *b) 
-{
-    return (char *) b->data + b->size;
+    if (b->source == OFPBUF_MALLOC && ofpbuf_data(b) == ofpbuf_base(b)) {
+        p = ofpbuf_data(b);
+    } else {
+        p = xmemdup(ofpbuf_data(b), ofpbuf_size(b));
+        if (b->source == OFPBUF_MALLOC) {
+            free(ofpbuf_base(b));
+        }
+    }
+    ofpbuf_set_base(b, NULL);
+    ofpbuf_set_data(b, NULL);
+    return p;
 }
 
-/* Returns the byte following the last byte allocated for use (but not
- * necessarily in use) by 'b'. */
-void *
-ofpbuf_end(const struct ofpbuf *b) 
+/* Returns a string that describes some of 'b''s metadata plus a hex dump of up
+ * to 'maxbytes' from the start of the buffer. */
+char *
+ofpbuf_to_string(const struct ofpbuf *b, size_t maxbytes)
 {
-    return (char *) b->base + b->allocated;
+    struct ds s;
+
+    ds_init(&s);
+    ds_put_format(&s, "size=%"PRIu32", allocated=%"PRIu32", head=%"PRIuSIZE", tail=%"PRIuSIZE"\n",
+                  ofpbuf_size(b), b->allocated,
+                  ofpbuf_headroom(b), ofpbuf_tailroom(b));
+    ds_put_hex_dump(&s, ofpbuf_data(b), MIN(ofpbuf_size(b), maxbytes), 0, false);
+    return ds_cstr(&s);
 }
 
-/* Clears any data from 'b'. */
+/* Removes each of the "struct ofpbuf"s on 'list' from the list and frees
+ * them.  */
 void
-ofpbuf_clear(struct ofpbuf *b) 
+ofpbuf_list_delete(struct list *list)
 {
-    b->data = b->base;
-    b->size = 0;
+    struct ofpbuf *b, *next;
+
+    LIST_FOR_EACH_SAFE (b, next, list_node, list) {
+        list_remove(&b->list_node);
+        ofpbuf_delete(b);
+    }
 }
 
-/* Removes 'size' bytes from the head end of 'b', which must contain at least
- * 'size' bytes of data.  Returns the first byte of data removed. */
-void *
-ofpbuf_pull(struct ofpbuf *b, size_t size) 
+static inline void
+ofpbuf_adjust_layer_offset(uint16_t *offset, int increment)
 {
-    void *data = b->data;
-    assert(b->size >= size);
-    b->data = (char*)b->data + size;
-    b->size -= size;
-    return data;
+    if (*offset != UINT16_MAX) {
+        *offset += increment;
+    }
 }
 
-/* If 'b' has at least 'size' bytes of data, removes that many bytes from the
- * head end of 'b' and returns the first byte removed.  Otherwise, returns a
- * null pointer without modifying 'b'. */
+/* Adjust the size of the l2_5 portion of the ofpbuf, updating the l2
+ * pointer and the layer offsets.  The caller is responsible for
+ * modifying the contents. */
 void *
-ofpbuf_try_pull(struct ofpbuf *b, size_t size) 
+ofpbuf_resize_l2_5(struct ofpbuf *b, int increment)
 {
-    return b->size >= size ? ofpbuf_pull(b, size) : NULL;
+    if (increment >= 0) {
+        ofpbuf_push_uninit(b, increment);
+    } else {
+        ofpbuf_pull(b, -increment);
+    }
+
+    b->frame = ofpbuf_data(b);
+    /* Adjust layer offsets after l2_5. */
+    ofpbuf_adjust_layer_offset(&b->l3_ofs, increment);
+    ofpbuf_adjust_layer_offset(&b->l4_ofs, increment);
+
+    return b->frame;
 }
 
-/* Returns a string that describes some of 'b''s metadata plus a hex dump of up
- * to 'maxbytes' from the start of the buffer. */
-char *
-ofpbuf_to_string(const struct ofpbuf *b, size_t maxbytes)
+/* Adjust the size of the l2 portion of the ofpbuf, updating the l2
+ * pointer and the layer offsets.  The caller is responsible for
+ * modifying the contents. */
+void *
+ofpbuf_resize_l2(struct ofpbuf *b, int increment)
 {
-    struct ds s;
-
-    ds_init(&s);
-    ds_put_format(&s, "size=%zu, allocated=%zu, head=%zu, tail=%zu\n",
-                  b->size, b->allocated,
-                  ofpbuf_headroom(b), ofpbuf_tailroom(b));
-    ds_put_hex_dump(&s, b->data, MIN(b->size, maxbytes), 0, false);
-    return ds_cstr(&s);
+    ofpbuf_resize_l2_5(b, increment);
+    ofpbuf_adjust_layer_offset(&b->l2_5_ofs, increment);
+    return b->frame;
 }