Try to make the MBUF_FRAG_TEST code work better.

- Don't try to fragment the packet if it's smaller than mbuf_frag_size.
- Preserve the size of the mbuf chain which is modified by m_split().
- Check that m_split() didn't return NULL.
- Make it so we don't end up with two M_PKTHDR mbuf in the chain.
- Use m->m_pkthdr.len instead of m->m_len so that we fragment the whole
  chain and not just the first mbuf.
- Fix a nearby style bug and rework the logic of the loops so that it's
  more clear.

This is still not quite right, because we're clearly abusing m_split() to
do something it was not designed for, but at least it works now.  We
should probably move this code into a m_fragment() function when it's
correct.

1 files changed, 10 insertions, 12 deletions

diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c
index 02fb2d3..c00ac4c 100644
--- a/sys/netinet/ip_output.c
+++ b/sys/netinet/ip_output.c
@@ -1021,25 +1021,23 @@ pass:
 #endif
 
 #ifdef MBUF_FRAG_TEST
-		if (mbuf_frag_size) {
+		if (mbuf_frag_size && m->m_pkthdr.len > mbuf_frag_size) {
 			struct mbuf *m1, *m2;
-			int length;
+			int length, tmp;
 
-			length = m->m_len;
+			tmp = length = m->m_pkthdr.len;
 
-			while (1) {
-				length -= mbuf_frag_size;
-					if (length < 1)
-						break;
+			while ((length -= mbuf_frag_size) >= 1) {
 				m1 = m_split(m, length, M_DONTWAIT);
+				if (m1 == NULL)
+					break;
+				m1->m_flags &= ~M_PKTHDR;
 				m2 = m;
-				while (1) {
-					if (m2->m_next == NULL)
-						break;
+				while (m2->m_next != NULL)
 					m2 = m2->m_next;
-				}
-			m2->m_next = m1;
+				m2->m_next = m1;
 			}
+			m->m_pkthdr.len = tmp;
 		}
 #endif
 		error = (*ifp->if_output)(ifp, m,