Date: Mon, 23 Feb 2004 18:25:49 +0200 From: Alexander Motin <mav@alkar.net> To: freebsd-net@freebsd.org, freebsd-ipfw@freebsd.org Subject: Re: Generating 'Fragment Needed but DF was Set' ICMP & Dummynet Message-ID: <c1d9id$10qf$1@pandora.alkar.net> In-Reply-To: <c0soic$1njq$2@pandora.alkar.net.lucky.freebsd.net> References: <c0soic$1njq$2@pandora.alkar.net.lucky.freebsd.net>
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--------------080204090202030100030402
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Here are my patches for this problem for FreeBSD 4.8 and 5.2.
Review them please.
Alexander Motin wrote:
> I observe a strange thing. When I create dummynet pipe on output router
> interface with lower MTU system stops to generate 'Fragment Needed but
> DF was Set' ICMP in cases when it must. If I create this pipe on
> incoming interface there is no problem.
>
> I check this on many routers under 4.8 and 5.2 FreeBSD.
>
> Is this a bug or feature? :) How pipes can be created leaving ICMP
> generation working?
--
Alexander Motin
--------------080204090202030100030402
Content-Type: text/plain;
name="dn_df_48.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
filename="dn_df_48.patch"
--- ip_dummynet.c.orig Wed May 28 01:36:02 2003
+++ ip_dummynet.c Sat Feb 21 12:49:11 2004
@@ -81,6 +81,7 @@
#include <netinet/ip_fw.h>
#include <netinet/ip_dummynet.h>
#include <netinet/ip_var.h>
+#include <netinet/ip_icmp.h>
#include <netinet/if_ether.h> /* for struct arpcom */
#include <net/bridge.h>
@@ -407,6 +408,9 @@
transmit_event(struct dn_pipe *pipe)
{
struct dn_pkt *pkt ;
+ struct mbuf *mcopy;
+ struct ip *ip;
+ int error, type, code;
while ( (pkt = pipe->head) && DN_KEY_LEQ(pkt->output_time, curr_time) ) {
/*
@@ -426,7 +430,39 @@
*/
switch (pkt->dn_dir) {
case DN_TO_IP_OUT:
- (void)ip_output((struct mbuf *)pkt, NULL, NULL, 0, NULL, NULL);
+ MGET(mcopy, M_DONTWAIT, pkt->dn_m->m_type);
+ if (mcopy != NULL && !m_dup_pkthdr(mcopy, pkt->dn_m, M_DONTWAIT)) {
+ m_free(mcopy);
+ mcopy = NULL;
+ }
+ if (mcopy != NULL) {
+ ip = mtod(pkt->dn_m, struct ip *);
+ mcopy->m_len = imin((ip->ip_hl << 2) + 8,
+ (int)ip->ip_len);
+ m_copydata(pkt->dn_m, 0, mcopy->m_len, mtod(mcopy, caddr_t));
+ }
+
+ error = ip_output((struct mbuf *)pkt, NULL, NULL, 0, NULL, NULL);
+
+ if (mcopy != NULL) {
+ switch (error) {
+ case ENETUNREACH:
+ case EHOSTUNREACH:
+ case ENETDOWN:
+ case EHOSTDOWN:
+ type = ICMP_UNREACH;
+ code = ICMP_UNREACH_HOST;
+ icmp_error(mcopy, type, code, 0, pkt->ifp);
+ break;
+ case EMSGSIZE:
+ type = ICMP_UNREACH;
+ code = ICMP_UNREACH_NEEDFRAG;
+ icmp_error(mcopy, type, code, 0, pkt->ifp);
+ break;
+ default:
+ m_freem(mcopy);
+ };
+ };
rt_unref (pkt->ro.ro_rt) ;
break ;
--------------080204090202030100030402
Content-Type: text/plain;
name="dn_df_52.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
filename="dn_df_52.patch"
--- ip_dummynet.c.orig Mon Dec 8 11:50:54 2003
+++ ip_dummynet.c Sat Feb 21 12:17:44 2004
@@ -73,6 +73,7 @@
#include <netinet/ip_fw.h>
#include <netinet/ip_dummynet.h>
#include <netinet/ip_var.h>
+#include <netinet/ip_icmp.h>
#include <netinet/if_ether.h> /* for struct arpcom */
#include <net/bridge.h>
@@ -426,6 +427,9 @@
transmit_event(struct dn_pipe *pipe)
{
struct dn_pkt *pkt ;
+ struct mbuf *mcopy;
+ struct ip *ip;
+ int error, type, code;
DUMMYNET_LOCK_ASSERT();
@@ -449,7 +453,39 @@
*/
switch (pkt->dn_dir) {
case DN_TO_IP_OUT:
- (void)ip_output((struct mbuf *)pkt, NULL, NULL, 0, NULL, NULL);
+ MGET(mcopy, M_DONTWAIT, pkt->dn_m->m_type);
+ if (mcopy != NULL && !m_dup_pkthdr(mcopy, pkt->dn_m, M_DONTWAIT)) {
+ m_free(mcopy);
+ mcopy = NULL;
+ }
+ if (mcopy != NULL) {
+ ip = mtod(pkt->dn_m, struct ip *);
+ mcopy->m_len = imin((ip->ip_hl << 2) + 8,
+ (int)ip->ip_len);
+ m_copydata(pkt->dn_m, 0, mcopy->m_len, mtod(mcopy, caddr_t));
+ }
+
+ error = ip_output((struct mbuf *)pkt, NULL, NULL, 0, NULL, NULL);
+
+ if (mcopy != NULL) {
+ switch (error) {
+ case ENETUNREACH:
+ case EHOSTUNREACH:
+ case ENETDOWN:
+ case EHOSTDOWN:
+ type = ICMP_UNREACH;
+ code = ICMP_UNREACH_HOST;
+ icmp_error(mcopy, type, code, 0, pkt->ifp);
+ break;
+ case EMSGSIZE:
+ type = ICMP_UNREACH;
+ code = ICMP_UNREACH_NEEDFRAG;
+ icmp_error(mcopy, type, code, 0, pkt->ifp);
+ break;
+ default:
+ m_freem(mcopy);
+ };
+ };
rt_unref (pkt->ro.ro_rt, __func__) ;
break ;
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