Re: [uml-devel] regression: pcap broken in 2.6.20.x

[Antoine Martin <antoine@nagafix.co.uk>]

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Antoine Martin wrote:
> Jeff Dike wrote:
>> On Fri, Apr 27, 2007 at 04:21:11PM +0100, Antoine Martin wrote:
>>> Question remains as to why the mac address was the same until 2.6.20 and
>>> is now different.
>> We started providing randomized MACs at bootup instead of deriving
>> them from the IP when the interface was brought up.  The old behavior
>> broke when distros started bringing interfaces up without assigning
>> IPs to them.
> 
>>> Except, pcap doesn't have the option.
>> Hmmm that would be a problem.
> :)
> I've got a patch - coming soon (tm)
Attached.

Not sure which approach is best:

1) this one requires a command line like:
"vmlinux eth0=pcap,eth0,,mac=00:01:02:03:04:05"

- --- a/arch/um/drivers/pcap_kern.c   2007-02-04 18:44:54.000000000 +0000
+++ b/arch/um/drivers/pcap_kern.c   2007-04-27 17:40:15.000000000 +0100
@@ -15,6 +15,7 @@
        int promisc;
        int optimize;
        char *filter;
+       char *mac;
 };

 void pcap_init(struct net_device *dev, void *data)
@@ -56,17 +57,18 @@
 int pcap_setup(char *str, char **mac_out, void *data)
 {
        struct pcap_init *init = data;
- -       char *remain, *host_if = NULL, *options[2] = { NULL, NULL };
+       char *remain, *host_if = NULL, *options[3] = { NULL, NULL, NULL };
        int i;

        *init = ((struct pcap_init)
                { .host_if      = "eth0",
                  .promisc      = 1,
                  .optimize     = 0,
- -                 .filter       = NULL });
+                 .filter       = NULL,
+                 .mac          = "00:00:00:00:00:00" });

        remain = split_if_spec(str, &host_if, &init->filter,
- -                              &options[0], &options[1], NULL);
+                              &options[0], &options[1], &options[2], NULL);
        if(remain != NULL){
                printk(KERN_ERR "pcap_setup - Extra garbage on "
                       "specification : '%s'\n", remain);
@@ -87,6 +89,10 @@
                        init->optimize = 1;
                else if(!strcmp(options[i], "nooptimize"))
                        init->optimize = 0;
+               else if(!strncmp(options[i], "mac=", 4) &&
strlen(options[i])==21) {
+                       strncpy(init->mac, options[i]+4, 17);
+                       *mac_out = init->mac;
+               }
                else printk("pcap_setup : bad option - '%s'\n", options[i]);
        }



2) or this one: which just assumes that the mac address is any option
that isn't [no]promisc or [no]optimize and is 17 characters long (I
don't see much point in doing extra checks since this is check in
setup_ether_xx later on)

- --- /uml/kernels/src/linux-2.6.20.9-amd64/arch/um/drivers/pcap_kern.c
2007-02-04 18:44:54.000000000 +0000
+++ pcap_kern.c 2007-04-27 17:45:31.000000000 +0100
@@ -15,6 +15,7 @@
        int promisc;
        int optimize;
        char *filter;
+       char *mac;
 };

 void pcap_init(struct net_device *dev, void *data)
@@ -56,17 +57,18 @@
 int pcap_setup(char *str, char **mac_out, void *data)
 {
        struct pcap_init *init = data;
- -       char *remain, *host_if = NULL, *options[2] = { NULL, NULL };
+       char *remain, *host_if = NULL, *options[3] = { NULL, NULL, NULL };
        int i;

        *init = ((struct pcap_init)
                { .host_if      = "eth0",
                  .promisc      = 1,
                  .optimize     = 0,
- -                 .filter       = NULL });
+                 .filter       = NULL,
+                 .mac          = "00:00:00:00:00:00" });

        remain = split_if_spec(str, &host_if, &init->filter,
- -                              &options[0], &options[1], NULL);
+                              &options[0], &options[1], &options[2], NULL);
        if(remain != NULL){
                printk(KERN_ERR "pcap_setup - Extra garbage on "
                       "specification : '%s'\n", remain);
@@ -87,6 +89,11 @@
                        init->optimize = 1;
                else if(!strcmp(options[i], "nooptimize"))
                        init->optimize = 0;
+               else if(strlen(options[i])==17) {
+                       //a mac address is always 17 characters long
+                       strncpy(init->mac, options[i], 17);
+                       *mac_out = init->mac;
+               }
                else printk("pcap_setup : bad option - '%s'\n", options[i]);
        }
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