xref: /freebsd/sys/netipsec/ipsec_mbuf.c (revision 88768458d21c0a0eef6cf91053630b94a58fef3c)

/*	$FreeBSD$	*/

/*
 * IPsec-specific mbuf routines.
 */

#include "opt_param.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/socket.h>

#include <net/route.h>
#include <netinet/in.h>

#include <netipsec/ipsec.h>

extern	struct mbuf *m_getptr(struct mbuf *, int, int *);

/*
 * Create a writable copy of the mbuf chain.  While doing this
 * we compact the chain with a goal of producing a chain with
 * at most two mbufs.  The second mbuf in this chain is likely
 * to be a cluster.  The primary purpose of this work is to create
 * a writable packet for encryption, compression, etc.  The
 * secondary goal is to linearize the data so the data can be
 * passed to crypto hardware in the most efficient manner possible.
 */
struct mbuf *
m_clone(struct mbuf *m0)
{
	struct mbuf *m, *mprev;

	KASSERT(m0 != NULL, ("m_clone: null mbuf"));

	mprev = NULL;
	for (m = m0; m != NULL; m = mprev->m_next) {
		/*
		 * Regular mbufs are ignored unless there's a cluster
		 * in front of it that we can use to coalesce.  We do
		 * the latter mainly so later clusters can be coalesced
		 * also w/o having to handle them specially (i.e. convert
		 * mbuf+cluster -> cluster).  This optimization is heavily
		 * influenced by the assumption that we're running over
		 * Ethernet where MCBYTES is large enough that the max
		 * packet size will permit lots of coalescing into a
		 * single cluster.  This in turn permits efficient
		 * crypto operations, especially when using hardware.
		 */
		if ((m->m_flags & M_EXT) == 0) {
			if (mprev && (mprev->m_flags & M_EXT) &&
			    m->m_len <= M_TRAILINGSPACE(mprev)) {
				/* XXX: this ignores mbuf types */
				memcpy(mtod(mprev, caddr_t) + mprev->m_len,
				       mtod(m, caddr_t), m->m_len);
				mprev->m_len += m->m_len;
				mprev->m_next = m->m_next;	/* unlink from chain */
				m_free(m);			/* reclaim mbuf */
				newipsecstat.ips_mbcoalesced++;
			} else {
				mprev = m;
			}
			continue;
		}
		/*
		 * Cluster'd mbufs are left alone (for now).
		 */
		if (!MEXT_IS_REF(m)) {
			mprev = m;
			continue;
		}
		/*
		 * Not writable, replace with a copy or coalesce with
		 * the previous mbuf if possible (since we have to copy
		 * it anyway, we try to reduce the number of mbufs and
		 * clusters so that future work is easier).
		 */
		/* XXX why can M_PKTHDR be set past the first mbuf? */
		KASSERT(m->m_flags & M_EXT,
			("m_clone: m_flags 0x%x", m->m_flags));
		/* NB: we only coalesce into a cluster */
		if (mprev == NULL || (mprev->m_flags & M_EXT) == 0 ||
		    m->m_len > M_TRAILINGSPACE(mprev)) {
			struct mbuf *n;

			/*
			 * Allocate a new page, copy the data to the front
			 * and release the reference to the old page.
			 */
			n = m_getcl(M_DONTWAIT, m->m_type, m->m_flags);
			if (n == NULL) {
				m_freem(m0);
				return (NULL);
			}
			if (mprev == NULL && (m->m_flags & M_PKTHDR))
				M_COPY_PKTHDR(n, m);
			memcpy(mtod(n, caddr_t), mtod(m, caddr_t), m->m_len);
			n->m_len = m->m_len;
			n->m_next = m->m_next;
			if (mprev == NULL)
				m0 = n;			/* new head of chain */
			else
				mprev->m_next = n;	/* replace old mbuf */
			m_free(m);			/* release old mbuf */
			mprev = n;
			newipsecstat.ips_clcopied++;
		} else {
			/* XXX: this ignores mbuf types */
			memcpy(mtod(mprev, caddr_t) + mprev->m_len,
			       mtod(m, caddr_t), m->m_len);
			mprev->m_len += m->m_len;
			mprev->m_next = m->m_next;	/* unlink from chain */
			m_free(m);			/* reclaim mbuf */
			newipsecstat.ips_clcoalesced++;
		}
	}
	return (m0);
}

/*
 * Make space for a new header of length hlen at offset off
 * in the packet.  When doing this we allocate new mbufs only
 * when absolutely necessary.  The mbuf where the new header
 * is to go is returned together with an offset into the mbuf.
 * If NULL is returned then the mbuf chain may have been modified;
 * the caller is assumed to always free the chain.
 */
struct mbuf *
m_makespace(struct mbuf *m0, int skip, int hlen, int *off)
{
	struct mbuf *m;
	unsigned remain;

	KASSERT(m0 != NULL, ("m_dmakespace: null mbuf"));
	KASSERT(hlen < MHLEN, ("m_makespace: hlen too big: %u", hlen));

	for (m = m0; m && skip > m->m_len; m = m->m_next)
		skip -= m->m_len;
	if (m == NULL)
		return (NULL);
	/*
	 * At this point skip is the offset into the mbuf m
	 * where the new header should be placed.  Figure out
	 * if there's space to insert the new header.  If so,
	 * and copying the remainder makese sense then do so.
	 * Otherwise insert a new mbuf in the chain, splitting
	 * the contents of m as needed.
	 */
	remain = m->m_len - skip;		/* data to move */
	/* XXX code doesn't handle clusters XXX */
	KASSERT(remain < MLEN, ("m_makespace: remainder too big: %u", remain));
	if (hlen > M_TRAILINGSPACE(m)) {
		struct mbuf *n;

		/*
		 * Not enough space in m, split the contents
		 * of m, inserting new mbufs as required.
		 *
		 * NB: this ignores mbuf types.
		 */
		MGET(n, M_DONTWAIT, MT_DATA);
		if (n == NULL)
			return (NULL);
		n->m_next = m->m_next;		/* splice new mbuf */
		m->m_next = n;
		newipsecstat.ips_mbinserted++;
		if (hlen <= M_TRAILINGSPACE(m) + remain) {
			/*
			 * New header fits in the old mbuf if we copy
			 * the remainder; just do the copy to the new
			 * mbuf and we're good to go.
			 */
			memcpy(mtod(n, caddr_t),
			       mtod(m, caddr_t) + skip, remain);
			n->m_len = remain;
			m->m_len = skip + hlen;
			*off = skip;
		} else {
			/*
			 * No space in the old mbuf for the new header.
			 * Make space in the new mbuf and check the
			 * remainder'd data fits too.  If not then we
			 * must allocate an additional mbuf (yech).
			 */
			n->m_len = 0;
			if (remain + hlen > M_TRAILINGSPACE(n)) {
				struct mbuf *n2;

				MGET(n2, M_DONTWAIT, MT_DATA);
				/* NB: new mbuf is on chain, let caller free */
				if (n2 == NULL)
					return (NULL);
				n2->m_len = 0;
				memcpy(mtod(n2, caddr_t),
				       mtod(m, caddr_t) + skip, remain);
				n2->m_len = remain;
				/* splice in second mbuf */
				n2->m_next = n->m_next;
				n->m_next = n2;
				newipsecstat.ips_mbinserted++;
			} else {
				memcpy(mtod(n, caddr_t) + hlen,
				       mtod(m, caddr_t) + skip, remain);
				n->m_len += remain;
			}
			m->m_len -= remain;
			n->m_len += hlen;
			m = n;			/* header is at front ... */
			*off = 0;		/* ... of new mbuf */
		}
	} else {
		/*
		 * Copy the remainder to the back of the mbuf
		 * so there's space to write the new header.
		 */
		/* XXX can this be memcpy? does it handle overlap? */
		ovbcopy(mtod(m, caddr_t) + skip,
			mtod(m, caddr_t) + skip + hlen, remain);
		m->m_len += hlen;
		*off = skip;
	}
	m0->m_pkthdr.len += hlen;		/* adjust packet length */
	return m;
}

/*
 * m_pad(m, n) pads <m> with <n> bytes at the end. The packet header
 * length is updated, and a pointer to the first byte of the padding
 * (which is guaranteed to be all in one mbuf) is returned.
 */
caddr_t
m_pad(struct mbuf *m, int n)
{
	register struct mbuf *m0, *m1;
	register int len, pad;
	caddr_t retval;

	if (n <= 0) {  /* No stupid arguments. */
		DPRINTF(("m_pad: pad length invalid (%d)\n", n));
		m_freem(m);
		return NULL;
	}

	len = m->m_pkthdr.len;
	pad = n;
	m0 = m;

	while (m0->m_len < len) {
KASSERT(m0->m_next != NULL, ("m_pad: m0 null, len %u m_len %u", len, m0->m_len));/*XXX*/
		len -= m0->m_len;
		m0 = m0->m_next;
	}

	if (m0->m_len != len) {
		DPRINTF(("m_pad: length mismatch (should be %d instead of %d)\n",
		    m->m_pkthdr.len, m->m_pkthdr.len + m0->m_len - len));

		m_freem(m);
		return NULL;
	}

	/* Check for zero-length trailing mbufs, and find the last one. */
	for (m1 = m0; m1->m_next; m1 = m1->m_next) {
		if (m1->m_next->m_len != 0) {
			DPRINTF(("m_pad: length mismatch (should be %d "
			    "instead of %d)\n",
			    m->m_pkthdr.len,
			    m->m_pkthdr.len + m1->m_next->m_len));

			m_freem(m);
			return NULL;
		}

		m0 = m1->m_next;
	}

	if (pad > M_TRAILINGSPACE(m0)) {
		/* Add an mbuf to the chain. */
		MGET(m1, M_DONTWAIT, MT_DATA);
		if (m1 == 0) {
			m_freem(m0);
			DPRINTF(("m_pad: unable to get extra mbuf\n"));
			return NULL;
		}

		m0->m_next = m1;
		m0 = m1;
		m0->m_len = 0;
	}

	retval = m0->m_data + m0->m_len;
	m0->m_len += pad;
	m->m_pkthdr.len += pad;

	return retval;
}

/*
 * Remove hlen data at offset skip in the packet.  This is used by
 * the protocols strip protocol headers and associated data (e.g. IV,
 * authenticator) on input.
 */
int
m_striphdr(struct mbuf *m, int skip, int hlen)
{
	struct mbuf *m1;
	int roff;

	/* Find beginning of header */
	m1 = m_getptr(m, skip, &roff);
	if (m1 == NULL)
		return (EINVAL);

	/* Remove the header and associated data from the mbuf. */
	if (roff == 0) {
		/* The header was at the beginning of the mbuf */
		newipsecstat.ips_input_front++;
		m_adj(m1, hlen);
		if ((m1->m_flags & M_PKTHDR) == 0)
			m->m_pkthdr.len -= hlen;
	} else if (roff + hlen >= m1->m_len) {
		struct mbuf *mo;

		/*
		 * Part or all of the header is at the end of this mbuf,
		 * so first let's remove the remainder of the header from
		 * the beginning of the remainder of the mbuf chain, if any.
		 */
		newipsecstat.ips_input_end++;
		if (roff + hlen > m1->m_len) {
			/* Adjust the next mbuf by the remainder */
			m_adj(m1->m_next, roff + hlen - m1->m_len);

			/* The second mbuf is guaranteed not to have a pkthdr... */
			m->m_pkthdr.len -= (roff + hlen - m1->m_len);
		}

		/* Now, let's unlink the mbuf chain for a second...*/
		mo = m1->m_next;
		m1->m_next = NULL;

		/* ...and trim the end of the first part of the chain...sick */
		m_adj(m1, -(m1->m_len - roff));
		if ((m1->m_flags & M_PKTHDR) == 0)
			m->m_pkthdr.len -= (m1->m_len - roff);

		/* Finally, let's relink */
		m1->m_next = mo;
	} else {
		/*
		 * The header lies in the "middle" of the mbuf; copy
		 * the remainder of the mbuf down over the header.
		 */
		newipsecstat.ips_input_middle++;
		bcopy(mtod(m1, u_char *) + roff + hlen,
		      mtod(m1, u_char *) + roff,
		      m1->m_len - (roff + hlen));
		m1->m_len -= hlen;
		m->m_pkthdr.len -= hlen;
	}
	return (0);
}

/*
 * Diagnostic routine to check mbuf alignment as required by the
 * crypto device drivers (that use DMA).
 */
void
m_checkalignment(const char* where, struct mbuf *m0, int off, int len)
{
	int roff;
	struct mbuf *m = m_getptr(m0, off, &roff);
	caddr_t addr;

	if (m == NULL)
		return;
	printf("%s (off %u len %u): ", where, off, len);
	addr = mtod(m, caddr_t) + roff;
	do {
		int mlen;

		if (((uintptr_t) addr) & 3) {
			printf("addr misaligned %p,", addr);
			break;
		}
		mlen = m->m_len;
		if (mlen > len)
			mlen = len;
		len -= mlen;
		if (len && (mlen & 3)) {
			printf("len mismatch %u,", mlen);
			break;
		}
		m = m->m_next;
		addr = m ? mtod(m, caddr_t) : NULL;
	} while (m && len > 0);
	for (m = m0; m; m = m->m_next)
		printf(" [%p:%u]", mtod(m, caddr_t), m->m_len);
	printf("\n");
}