add an ipv6 "don't fragment" flag to mbufs for ip6_output to use.

if you need to send an ipv6 packet with ip6_send(), there's no DF
bit in an ipv6 packet and no way to pass the ip6 options to ip6_output
to tell it to not allow fragmentation. this adds an M_IPV6_DF_OUT
"checksum" flag so something creating ipv6 packets a long way from
ip6_output can easily tell it to not allow fragmentation.

grumbling and ok claudio@

diff --git a/sys/netinet6/ip6_output.c b/sys/netinet6/ip6_output.c
index 03fc4fa..4818d7c 100644 (file)
--- a/sys/netinet6/ip6_output.c
+++ b/sys/netinet6/ip6_output.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: ip6_output.c,v 1.232 2017/09/01 15:05:31 mpi Exp $    */
+/*     $OpenBSD: ip6_output.c,v 1.233 2018/02/11 00:24:13 dlg Exp $    */
 /*     $KAME: ip6_output.c,v 1.172 2001/03/25 09:55:56 itojun Exp $    */
 
 /*
@@ -656,7 +656,10 @@ reroute:
         */
        tlen = m->m_pkthdr.len;
 
-       if (opt && (opt->ip6po_flags & IP6PO_DONTFRAG))
+       if (ISSET(m->m_pkthdr.csum_flags, M_IPV6_DF_OUT)) {
+               CLR(m->m_pkthdr.csum_flags, M_IPV6_DF_OUT);
+               dontfrag = 1;
+       } else if (opt && ISSET(opt->ip6po_flags, IP6PO_DONTFRAG))
                dontfrag = 1;
        else
                dontfrag = 0;

diff --git a/sys/sys/mbuf.h b/sys/sys/mbuf.h
index 825cc80..14a43b4 100644 (file)
--- a/sys/sys/mbuf.h
+++ b/sys/sys/mbuf.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: mbuf.h,v 1.234 2018/02/09 02:26:33 patrick Exp $      */
+/*     $OpenBSD: mbuf.h,v 1.235 2018/02/11 00:24:13 dlg Exp $  */
 /*     $NetBSD: mbuf.h,v 1.19 1996/02/09 18:25:14 christos Exp $       */
 
 /*
@@ -224,12 +224,14 @@ struct mbuf {
 #define        M_ICMP_CSUM_OUT         0x0200  /* ICMP/ICMPv6 checksum needed */
 #define        M_ICMP_CSUM_IN_OK       0x0400  /* ICMP/ICMPv6 checksum verified */
 #define        M_ICMP_CSUM_IN_BAD      0x0800  /* ICMP/ICMPv6 checksum bad */
+#define        M_IPV6_DF_OUT           0x1000  /* don't fragment outgoing IPv6 */
 
 #ifdef _KERNEL
 #define MCS_BITS \
     ("\20\1IPV4_CSUM_OUT\2TCP_CSUM_OUT\3UDP_CSUM_OUT\4IPV4_CSUM_IN_OK" \
     "\5IPV4_CSUM_IN_BAD\6TCP_CSUM_IN_OK\7TCP_CSUM_IN_BAD\10UDP_CSUM_IN_OK" \
-    "\11UDP_CSUM_IN_BAD\12ICMP_CSUM_OUT\13ICMP_CSUM_IN_OK\14ICMP_CSUM_IN_BAD")
+    "\11UDP_CSUM_IN_BAD\12ICMP_CSUM_OUT\13ICMP_CSUM_IN_OK\14ICMP_CSUM_IN_BAD" \
+    "\15IPV6_NODF_OUT")
 #endif
 
 /* mbuf types */