Re: routing bug?

From: Luigi Rizzo <rizzo_at_icir.org>
Date: Fri, 7 May 2004 17:30:34 -0700
On Fri, May 07, 2004 at 11:12:53PM +0200, Andre Oppermann wrote:
> Mike Tancsa wrote:
...
> I hope this explains the effect you are seeing.  A backport or MFC of
> the protocol cloning removal is not possible and is a rather extensive
> change to the network stack which is outside of the RELENG_4 scope.

actually my student Alessandro Cerri did just that, though I am
not sure if there is interest in committing it...
It all depends on what's the expected lifetime of 4.x
and whether 5.x gets "up to speed" reasonably...

cheers
luigi

> There is one easy hack you can do for UDP sockets.  That is you simply
> RTFREE() the rtentry pointed to by the inpcb early on in udp_output()
> just to let a new one be reaquired later on.  If it is NULL the code
> will simply redo the routing table lookup and store a new pointer the
> rtentry.  With this every time you send a UDP packet you'll get the
> corret route.  A little bit more extensive hack would simply avoid
> storing the rtentry pointer in the inpcb at all.  I once did this for
> an RELENG_4 machine without any ill effects (if done correctly).  The
> same applies to OpenBSD and NetBSD.
> 
> -- 
> Andre
> 
> 
> >         ---Mike
> > 
> > At 09:59 AM 07/05/2004, Gabor wrote:
> > 
> >> I am experiencing some weird routing phenomena.
> >> When I open a UDP socket and send datagrams to an address(172.30.1.1)
> >> and then remove that route(route delete 172.30.1.1) then my packets
> >> switch from going out the route specific interface(rl0) to going out
> >> the default interface(fxp0).  This is as expected.  Then I add back
> >> the route (route add 172.30.1.1 10.0.2.2) and the packets swing back
> >> to the route specific interface(rl0).  However, if I bind my socket to
> >> a source address(172.16.24.33), when I remove the route and then add
> >> it back, the packets continue to go out the default interface(fxp0)
> >> instead of going out the route specific interface(rl0).
> >>
> >> This is on 4.9 STABLE.  I was unable to reproduce this on 5.2.1.  What
> >> changes have there been that haven't been MFC'ed?
> >>
> >> =0= udp-test # netstat -nr
> >> Routing tables
> >>
> >> Internet:
> >> Destination        Gateway            Flags    Refs      Use  Netif 
> >> Expire
> >> default            192.168.43.1       UGSc        2     2440   fxp0
> >> 10.0.2/24          link#1             UC          2        0    rl0
> >> 10.0.2.1           00:50:fc:32:52:a7  UHLW        0        2    lo0
> >> 10.0.2.2           00:0e:0c:05:09:19  UHLW        1        3    
> >> rl0     69
> >> 172.0.0.1          172.0.0.1          UH          0        0    lo0
> >> 172.30.1.1         10.0.2.2           UGHS        0        0    rl0
> >> 192.168.7          link#1             UC          0        0    rl0
> >> 192.168.43         link#2             UC          4        0   fxp0
> >> 192.168.43.1       00:50:bf:33:63:70  UHLW        4    56111   fxp0   
> >> 1079
> >> 192.168.43.31      link#2             UHLW        1      249   fxp0
> >> 192.168.43.157     00:a0:c9:4b:a5:f4  UHLW        6  2168880   fxp0    
> >> 771
> >> 192.168.43.242     link#2             UHLW        1   718878   fxp0
> >>
> >> =0= udp-test # ifconfig
> >> rl0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
> >>         inet 192.168.7.2 netmask 0xffffff00 broadcast 192.168.7.255
> >>         inet 10.0.2.1 netmask 0xffffff00 broadcast 10.0.2.255
> >>         ether 00:50:fc:32:52:a7
> >>         media: Ethernet 10baseT/UTP
> >>         status: active
> >> fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
> >>         inet 192.168.43.26 netmask 0xffffff00 broadcast 192.168.43.255
> >>         ether 00:01:80:3d:b4:4f
> >>         media: Ethernet autoselect (100baseTX <full-duplex>)
> >>         status: active
> >> ppp0: flags=8010<POINTOPOINT,MULTICAST> mtu 1500
> >> faith0: flags=8002<BROADCAST,MULTICAST> mtu 1500
> >> ds0: flags=8008<LOOPBACK,MULTICAST> mtu 65532
> >> lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
> >>         inet 172.16.24.33 netmask 0xffff0000
> >>         inet 172.0.0.1 netmask 0xffff0000
> >> tun0: flags=8010<POINTOPOINT,MULTICAST> mtu 1500
> >>
> >> =0= udp-test # cat udp-test.c
> >> #include <sys/types.h>
> >> #include <sys/time.h>
> >> #include <sys/socket.h>
> >> #include <netinet/in.h>
> >> #include <netdb.h>
> >> #include <unistd.h>
> >> #include <stdio.h>
> >> #include <stdlib.h>
> >> #include <string.h>
> >> #include <ctype.h>
> >>
> >> int send_pkt(unsigned char *src, unsigned char *dest, unsigned short 
> >> port);
> >>
> >> int
> >> main(int argc, char **argv)
> >> {
> >>     unsigned a, b, c, d, a2, b2, c2, d2;
> >>     unsigned port;
> >>     unsigned char src[4], dest[4];
> >>
> >>
> >>     if (argc != 3) {
> >>         fprintf(stderr,
> >>                 "Usage: %s <source> <dest>:<port>\n",
> >>                 argv[0]);
> >>         return 1;
> >>     }
> >>
> >>     if (sscanf(argv[1], "%u.%u.%u.%u", &a, &b, &c, &d) == 4
> >>             && a < 256 && b < 256 && c < 256 && d < 256
> >>             && sscanf(argv[2], "%u.%u.%u.%u:%u", &a2, &b2, &c2, &d2, 
> >> &port) == 5
> >>             && a2 < 256 && b2 < 256 && c2 < 256 && d2 < 256 && port < 
> >> 65536) {
> >>         /* OK */
> >>         src[0]  = a;
> >>         src[1]  = b;
> >>         src[2]  = c;
> >>         src[3]  = d;
> >>         dest[0] = a2;
> >>         dest[1] = b2;
> >>         dest[2] = c2;
> >>         dest[3] = d2;
> >>         send_pkt(src, dest, port);
> >>     }
> >>     else {
> >>         fprintf(stderr,
> >>                 "Usage: %s <source> <dest>:<port>\n",
> >>                 argv[0]);
> >>         return 1;
> >>     }
> >>
> >>     return 0;
> >> }
> >>
> >> int
> >> send_pkt(unsigned char *src, unsigned char *dest, unsigned short port)
> >> {
> >>     int s, len, cnt, rc, on;
> >>     struct protoent *proto;
> >>     struct sockaddr_in to, from;
> >>     char data[1024];
> >>
> >>     if (!(proto = getprotobyname("udp"))) {
> >>         perror("getprotobyname");
> >>         return -1;
> >>     }
> >>
> >>     if ((s = socket(PF_INET, SOCK_DGRAM, proto->p_proto)) < 0) {
> >>         perror("socket");
> >>         return -1;
> >>     }
> >>     on = 1;
> >>
> >>     memset(&from, 0, sizeof from);
> >>     from.sin_family = AF_INET;
> >>     from.sin_port = htons(0);
> >>     memcpy(&from.sin_addr.s_addr, src, 4);
> >>     fprintf(stderr,
> >>             "bind:%d\n",
> >>             bind(s, (struct sockaddr*)&from, sizeof from));
> >>
> >>     memset(&to, 0, sizeof to);
> >>     to.sin_family = AF_INET;
> >>     to.sin_port = htons(port);
> >>     memcpy(&to.sin_addr.s_addr, dest, 4);
> >>     len = 58;
> >>     cnt = 0;
> >>     while (1) {
> >>         memset(data, cnt, len);
> >>         rc = sendto(s, data, len, 0, (struct sockaddr*)&to, sizeof to);
> >>         if (rc < 0)
> >>             perror("");
> >>         fprintf(stderr, "%d %d\n", rc, cnt);
> >>         sleep(5);
> >>         ++cnt;
> >>     }
> >>     close(s);
> >>
> >>     return 0;
> >> }
> >>
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> > 
> > 
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> > 
> 
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Received on Fri May 07 2004 - 15:30:40 UTC

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