kern/62957: When created dummynet pipe on output routerinterface with lower MTU system stops to generate 'Fragment Needed but DF was Set' ICMP in cases when it must

[Alexander Motin]

The following reply was made to PR kern/62957; it has been noted by GNATS.

From: Alexander Motin <mav at alkar.net>
To: freebsd-gnats-submit at FreeBSD.org
Cc:  
Subject: Re: kern/62957: When created 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
Date: Mon, 23 Feb 2004 18:23:33 +0200

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 Here are my patches for this problem for 4.8 and 5.2.
 Review them please.
 
 -- 
 Alexander Motin mav at alkar.net
 ISP "Alkar-Teleport"
 
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  name="dn_df_48.patch"
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  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 ;
  
 
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  name="dn_df_52.patch"
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 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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