Function m_copypacket

freebsd/kern/uipc_mbuf.c:565–610

* Copy an entire packet, including header (which must be present). * An optimization of the common case `m_copym(m, 0, M_COPYALL, how)'. * Note that the copy is read-only, because clusters are not copied, * only their reference counts are incremented. * Preserve alignment of the first mbuf so if the creator has left * some room at the beginning (e.g. for inserting protocol headers) * the cop

 * the copies still have the room available.
 */
struct mbuf *
m_copypacket(struct mbuf *m, int how)
{
	struct mbuf *top, *n, *o;

	MBUF_CHECKSLEEP(how);
	n = m_get(how, m->m_type);
	top = n;
	if (n == NULL)
		goto nospace;

	if (!m_dup_pkthdr(n, m, how))
		goto nospace;
	n->m_len = m->m_len;
	if (m->m_flags & (M_EXT|M_EXTPG)) {
		n->m_data = m->m_data;
		mb_dupcl(n, m);
	} else {
		n->m_data = n->m_pktdat + (m->m_data - m->m_pktdat );
		bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
	}

	m = m->m_next;
	while (m) {
		o = m_get(how, m->m_type);
		if (o == NULL)
			goto nospace;

		n->m_next = o;
		n = n->m_next;

		n->m_len = m->m_len;
		if (m->m_flags & (M_EXT|M_EXTPG)) {
			n->m_data = m->m_data;
			mb_dupcl(n, m);
		} else {
			bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
		}

		m = m->m_next;
	}
	return top;
nospace:
	m_freem(top);
	return (NULL);
}

static void
m_copyfromunmapped(const struct mbuf *m, int off, int len, caddr_t cp)