Netmap module fails to load on OpenWrt MIPS malta (Qemu)

[ratkaj]

Hello,

I'm trying to create a working netmap package for OpenWrt. With modifications to the provided Makefile netmap successfully compiles for various architectures supported by OpenWrt.

I want a working Qemu OpenWrt MIPS image for testing, however netmap module fails to start producing a error. Here is the dmesg from the point i tried to load netmap module.

dmesg.txt

I get the same results when i first unload all related modules before i load netmap, and also the same error is present on other architectures, for instance brcm2708 (raspberry)

Strace might show a clue.

strace.txt

And here is ifconfig.

ifconfig.txt

I will provide any requested info, and hopefully the new OpenWrt Makefile once everything is fixed and tested.

[vmaffione]

It seems that the malloc() call done by the netmap_init_bridges2() function fails, because the requested memory size (almost 147KB) is larger than the value of KMALLOC_MAX_SIZE macro, defined in include/linux/slab.h.

Can you try to print this macro to check how much it is in your VMs? In my physical machine the macro resolves to 8MB.

[ratkaj]

Apologies if i did this wrong, i still have a lot to learn. I patched the kernel source to print the macro at compile time. This is the result.

pragma message: KMALLOC_MAX_SIZE=(1UL << ((11 + 12 - 1) <= 17 ? (11 + 12 - 1) : 17))

[vmaffione]

No problems, but the easy way is to apply this patch:

diff --git a/LINUX/netmap_linux.c b/LINUX/netmap_linux.c
index 7c2c434..1697467 100644
--- a/LINUX/netmap_linux.c
+++ b/LINUX/netmap_linux.c
@@ -2454,6 +2454,7 @@ struct miscdevice netmap_cdevsw = { /* same name as FreeBSD */
 static int linux_netmap_init(void)
 {
        int err;
+       printk("KMALLOC_MAX_SIZE %u\n", KMALLOC_MAX_SIZE);
        /* Errors have negative values on linux. */
        err = -netmap_init();
        if (err) {

compile and reinsert the netmap module. You will see the result in the kernel log.

[ratkaj]

Thank you for your response. Here is the real value KMALLOC_MAX_SIZE 131072

[vmaffione]

Ok, and you see it is less than 147 KB, and that's why netmap_init_bridges2 fails.

As a consequence, you have an easy fix. Just apply these patches:

diff --git a/LINUX/netmap_linux.c b/LINUX/netmap_linux.c
index 7c2c434..6e656ab 100644
--- a/LINUX/netmap_linux.c
+++ b/LINUX/netmap_linux.c
@@ -1812,7 +1812,7 @@ netmap_pernet_init(struct net *net)
                return error;

        ns->net = net;
-       ns->num_bridges = 8;
+       ns->num_bridges = 4;
        ns->bridges = netmap_init_bridges2(ns->num_bridges);
        if (ns->bridges == NULL) {
                nm_bns_destroy(net, ns);

diff --git a/sys/dev/netmap/netmap_vale.c b/sys/dev/netmap/netmap_vale.c
index dcae261..d61521d 100644
--- a/sys/dev/netmap/netmap_vale.c
+++ b/sys/dev/netmap/netmap_vale.c
@@ -147,7 +147,7 @@ __FBSDID("$FreeBSD: head/sys/dev/netmap/netmap.c 257176 2013-10-26 17:58:36Z gle
 #define NM_BDG_BATCH_MAX       (NM_BDG_BATCH + NM_MULTISEG)
 /* NM_FT_NULL terminates a list of slots in the ft */
 #define NM_FT_NULL             NM_BDG_BATCH_MAX
-#define        NM_BRIDGES              8       /* number of bridges */
+#define        NM_BRIDGES              4       /* number of bridges */

 /*

[ratkaj]

Thank you for your great support, this has resolved the issue and all modules load.

There is however a issue when i call pkt-gen for testing.

# pkt-gen -i eth0 -f tx -l 60

678.781098 nm_open [847] NIOCREGIF failed: Device or resource busy eth0
678.783029 main [2436] Unable to open netmap:eth0: Device or resource busy
678.785100 main [2517] aborting

I will do some research to try and resolve the issue, of course any advice is welcomed. Once again thank you for your support. The original issue has been resolved.

[vmaffione]

Ok, I'm closing this.

For the other issue, check that your eth0 is "free", e.g. is not attached to a software bridge/openvswitch or similar.

In any case you can grep the code for EBUSY and put debug prints to see where the interface registration fails.