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Avoid using hard-coded MAC addresses and net_devices on TX path.
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This introduces a reverse-path routing system based on the path a packet was received on.
We return it to the source MAC address on the device it arrived on; this seems to be a
reasonable heuristic to follow provided we have symmetric paths in the network.

[TODO] Integration with the Linux neighbour cache and routing framework, but doing so
       without using the socket interface was going to take more time than I currently
       have to get this working.
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Matthew Huxtable committed Jul 1, 2014
1 parent bad3162 commit c57e0c5
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Showing 2 changed files with 42 additions and 108 deletions.
146 changes: 38 additions & 108 deletions src/kernel/net/udpserver.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,21 +24,10 @@

static __u16 __bitwise ip_id = 1;

/* stopgap measure until this info can be supplied by the full stack implementation */
//static unsigned char mac_them[] = {0x3c, 0x4a, 0x92, 0x77, 0xa7, 0x42};
static unsigned char mac_them[] = {0x00, 0x1b, 0x21, 0xab, 0xe2, 0x38}; // q208
static unsigned char mac_them2[] = {0x90, 0xe2, 0xba, 0x40, 0x8b, 0xc9};// q207
static unsigned char mac_them3[] = {0x90, 0xe2, 0xba, 0x27, 0xfb, 0xc8};// q201
static unsigned char mac_them4[] = {0x00, 0x1b, 0x21, 0xba, 0xa5, 0xfa};// nikola06
static unsigned char mac_them5[] = {0x00, 0x02, 0xc9, 0x3c, 0xa4, 0x41};// freestyle

#define NET_HDR_OVERHEAD \
sizeof(struct ethhdr) + sizeof(struct iphdr) + sizeof(struct udphdr) + 2

static struct net_device* dev = NULL;
static struct net_device* dev2 = NULL;
static struct net_device* dev3 = NULL;
static struct net_device* dev4 = NULL;

int udpserver_init_sendbuffers(struct request_state* req)
{
Expand Down Expand Up @@ -148,6 +137,20 @@ void set_up_ip_header(struct request_state* req, struct sk_buff* skb)
return;
}

static inline void copy_mac(unsigned char *from, unsigned char *to, size_t len)
{
int i;

if (unlikely(!from || !to))
return;
if (unlikely(len > ETH_ALEN))
len = ETH_ALEN;

for (i = 0; i < ETH_ALEN; i++)
to[i] = from[i];
return;
}

static inline
int set_up_eth_header(struct request_state* req, struct sk_buff* skb)
{
Expand All @@ -165,36 +168,11 @@ int set_up_eth_header(struct request_state* req, struct sk_buff* skb)
of indirection around the header_ops struct which contains pointers to
different functions for manipulating different headers depending on the
device struct dev. */
const void *mac_send;
struct net_device* devsend = NULL;
if (req->saddr == in_aton("10.10.0.5")) //q208
{
devsend = dev;
mac_send = &mac_them;
}
else if (req->saddr == in_aton("10.10.3.4")) //q207
{
devsend = dev4;
mac_send = &mac_them2;
}
else if (req->saddr == in_aton("10.10.0.1")) //q201
{
devsend = dev;
mac_send = &mac_them3;
}
else if (req->saddr == in_aton("10.10.2.25")) //nikola06
{
devsend = dev3;
mac_send = &mac_them4;
}
else // freestyle 10.10.1.4
{
devsend = dev2;
mac_send = &mac_them5;
}

unsigned char mac_send[ETH_ALEN];
struct net_device* devsend = req->devrcv;

copy_mac(req->mac_src, mac_send, ETH_ALEN);
err = dev_hard_header(skb, devsend, ETH_P_IP, mac_send, devsend->dev_addr, skb->len);

if (!err)
return err;

Expand Down Expand Up @@ -273,7 +251,15 @@ struct sk_buff* set_up_skb(struct request_state* req)

int udpserver_sendall(struct request_state* req)
{
struct sk_buff* skb = req->skb_tx;
struct sk_buff *skb;

if (unlikely(!req))
{
printk("No request?\n");
return -1;
}

skb = req->skb_tx;

/* get the net_device from the udp server's sock if we haven't already set it up
in global state*/
Expand All @@ -285,7 +271,7 @@ int udpserver_sendall(struct request_state* req)
rcu_read_lock();
for_each_net_rcu(ns)
{
dev = dev_get_by_name(ns, "eth4.2"); // 10.10.0.x
dev = dev_get_by_name(ns, "eth1.2"); // 10.10.0.x
if (dev)
break;
}
Expand All @@ -297,77 +283,14 @@ int udpserver_sendall(struct request_state* req)
return -1;
}
}

if (!dev2)
{
struct net* ns;
/* enumerate network namespaces until we find the one with the interface
we are interested in (eth0 here) */
rcu_read_lock();
for_each_net_rcu(ns)
{
dev2 = dev_get_by_name(ns, "eth1.2"); // 10.10.1.x
if (dev2)
break;
}
rcu_read_unlock();

if (!dev2)
{
printk("Uh oh! Cannot find the [second] network device in any class\n");
return -1;
}
}

if (!dev3)
{
struct net* ns;
/* enumerate network namespaces until we find the one with the interface
we are interested in (eth0 here) */
rcu_read_lock();
for_each_net_rcu(ns)
{
dev3 = dev_get_by_name(ns, "p801p1.2"); // 10.10.2.x
if (dev3)
break;
}
rcu_read_unlock();

if (!dev3)
{
printk("Uh oh! Cannot find the [second] network device in any class\n");
return -1;
}
}

if (!dev4)
{
struct net* ns;
/* enumerate network namespaces until we find the one with the interface
we are interested in (eth0 here) */
rcu_read_lock();
for_each_net_rcu(ns)
{
dev4 = dev_get_by_name(ns, "em1.2"); // 10.10.3.x
if (dev4)
break;
}
rcu_read_unlock();

if (!dev4)
{
printk("Uh oh! Cannot find the [second] network device in any class\n");
return -1;
}
}


/* Set up the pointer to the UDP headers before adding them */
req->udpheaders = (struct memcache_udp_header*)
skb_push(skb, sizeof(struct memcache_udp_header));
add_udp_headers(req);

skb->csum = csum_partial(skb->data, skb->len, 0x0);

set_up_udp_header(req, skb);
set_up_ip_header(req, skb);
set_up_eth_header(req, skb);
Expand All @@ -394,6 +317,7 @@ int do_kernel_rx_worker(struct request_state* req)
while (!kthread_should_stop() && ub_sys_running)
{
struct sk_buff* skb;
struct ethhdr *eth;
struct iphdr* iph;
struct udphdr* udph;

Expand Down Expand Up @@ -427,6 +351,12 @@ int do_kernel_rx_worker(struct request_state* req)

req->saddr = iph->saddr;
req->daddr = iph->daddr;

eth = (struct ethhdr*) (((char*)iph) - sizeof(struct ethhdr));
copy_mac(eth->h_source, req->mac_src, ETH_ALEN);

req->devrcv = skb->dev;

process_fastpath(req);

/* Fallthrough to make sure the SKB gets freed. We are done with it */
Expand Down
4 changes: 4 additions & 0 deletions src/request.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,9 @@
#define UNBUCKLE_REQUEST_H

#ifdef __KERNEL__
#include <linux/if_ether.h>
#include <linux/in.h>
#include <linux/netdevice.h>
#include <linux/socket.h>
#else
#include <arpa/inet.h>
Expand Down Expand Up @@ -72,6 +74,8 @@ struct request_state {
struct udphdr* udph;
__be32 saddr;
__be32 daddr;
unsigned char mac_src[ETH_ALEN];
struct net_device *devrcv;
#endif
};

Expand Down

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