//We need this function in addition to netpoll_wrapper_rx_handler() because pre-3.15 kernel versions
//will not call the rx handler for the packets matching the IP/port of our netpoll objects (expecting them
//to be handled in rx_hook that we don't use because it provides no way of reading the MAC address).
static void hook_receive_skb(void *pContext, struct sk_buff *skb)
{
int ulen;
struct iphdr *iph;
struct udphdr *uh;
struct netpoll_wrapper *pWrapper = (struct netpoll_wrapper *)pContext;
BUG_ON(!pWrapper);
if (skb->dev != pWrapper->pDeviceWithHandler)
return;
if (pWrapper->handle_arp && skb->protocol == htons(ETH_P_ARP))
{
netpoll_wrapper_handle_arp(pWrapper, skb);
return;
}
if (!parse_udp_packet(skb, &iph, &uh, &ulen))
return;
if (pWrapper->netpoll_obj.local_port && pWrapper->netpoll_obj.local_port == ntohs(uh->dest))
{
if ((ip_addr_as_int(pWrapper->netpoll_obj.local_ip) && ip_addr_as_int(pWrapper->netpoll_obj.local_ip) == iph->daddr) ||
(support_broadcast_packets && iph->daddr == 0xffffffff))
{
pWrapper->netpoll_obj.remote_port = ntohs(uh->source);
ip_addr_as_int(pWrapper->netpoll_obj.remote_ip) = iph->saddr;
memcpy(pWrapper->netpoll_obj.remote_mac, eth_hdr(skb)->h_source, sizeof(pWrapper->netpoll_obj.remote_mac));
if (pWrapper->pReceiveHandler)
pWrapper->pReceiveHandler(pWrapper, ntohs(uh->source), (char *)(uh + 1), ulen - sizeof(struct udphdr));
}
}
}
static void netpoll_wrapper_handle_arp(struct netpoll_wrapper *pWrapper, struct sk_buff *skb)
{
struct arphdr *arp;
unsigned char *arp_ptr;
unsigned char *sha;
__be32 sip, tip;
if (!pskb_may_pull(skb, arp_hdr_len(skb->dev)))
return;
skb_reset_network_header(skb);
skb_reset_transport_header(skb);
arp = arp_hdr(skb);
if ((arp->ar_hrd != htons(ARPHRD_ETHER) &&
arp->ar_hrd != htons(ARPHRD_IEEE802)) ||
arp->ar_pro != htons(ETH_P_IP) ||
arp->ar_op != htons(ARPOP_REQUEST))
return;
arp_ptr = (unsigned char *)(arp + 1);
/* save the location of the src hw addr */
sha = arp_ptr;
arp_ptr += skb->dev->addr_len;
memcpy(&sip, arp_ptr, 4);
arp_ptr += 4;
/* If we actually cared about dst hw addr,
it would get copied here */
arp_ptr += skb->dev->addr_len;
memcpy(&tip, arp_ptr, 4);
/* Should we ignore arp? */
if (ipv4_is_loopback(tip) || ipv4_is_multicast(tip))
return;
if (tip != ip_addr_as_int(pWrapper->netpoll_obj.local_ip))
return; //This ARP request is not for our IP address
for (int i = 0; i < ARRAY_SIZE(pWrapper->pending_arp_replies); i++)
{
if (!pWrapper->pending_arp_replies[i].valid)
{
pWrapper->pending_arp_replies[i].local_ip = tip;
pWrapper->pending_arp_replies[i].remote_ip = sip;
memcpy(pWrapper->pending_arp_replies[i].remote_mac, sha, sizeof(pWrapper->pending_arp_replies[i].remote_mac));
pWrapper->pending_arp_replies[i].valid = true;
break;
}
}
}
int kgdboe_io_init(const char *device_name, int port, const char *local_ip,
bool force_single_core)
{
int err;
u8 ipaddr[4];
spin_lock_init(&exception_lock);
s_pKgdboeNetpoll = netpoll_wrapper_create(device_name, port, local_ip);
if (!s_pKgdboeNetpoll)
return -EINVAL;
if (force_single_core) {
force_single_cpu_mode();
} else if (!nethook_initialize(s_pKgdboeNetpoll->pDeviceWithHandler)) {
printk(KERN_ERR "kgdboe: failed to guarantee cross-CPU network "
"API synchronization. Aborting. Try enabling "
"single-CPU mode.\n");
return -EINVAL;
}
err = kgdb_register_io_module(&kgdboe_io_ops);
if (err != 0) {
netpoll_wrapper_free(s_pKgdboeNetpoll);
s_pKgdboeNetpoll = NULL;
return err;
}
netpoll_wrapper_set_callback(s_pKgdboeNetpoll, kgdboe_rx_handler, NULL);
memcpy(ipaddr, &ip_addr_as_int(s_pKgdboeNetpoll->netpoll_obj.local_ip),
4);
printk(KERN_INFO "kgdboe: Successfully initialized. Use the following "
"gdb command to attach:\n");
printk(KERN_INFO "\ttarget remote udp:%d.%d.%d.%d:%d\n", ipaddr[0],
ipaddr[1], ipaddr[2], ipaddr[3],
s_pKgdboeNetpoll->netpoll_obj.local_port);
return 0;
}
//We need this in addition to hook_receive_skb() because not dropping a packet
//while stopped in gdb may invoke some processing functions from the network stack that
//would like to take resources owned by other cores (that are now stopped).
//We don't want to guess and pre-acquire those resources, so we just drop all packets while stopped in kgdb.
static rx_handler_result_t netpoll_wrapper_rx_handler(struct sk_buff **pskb)
{
struct netpoll_wrapper *pWrapper = (struct netpoll_wrapper *)(*pskb)->dev->rx_handler_data;
bool drop = false;
BUG_ON(!pWrapper);
if (pWrapper->drop_other_packets)
drop = true;
else
{
int ulen;
struct iphdr *iph;
struct udphdr *uh;
if (parse_udp_packet(*pskb, &iph, &uh, &ulen))
{
if (pWrapper->netpoll_obj.local_port && pWrapper->netpoll_obj.local_port == ntohs(uh->dest) && (ip_addr_as_int(pWrapper->netpoll_obj.local_ip) && ip_addr_as_int(pWrapper->netpoll_obj.local_ip) == iph->daddr))
{
//Otherwise Linux itself may handle it, reply with ICMP 'port not available' and force GDB to disconnect.
drop = true;
}
}
}
if (drop)
{
kfree_skb(*pskb);
return RX_HANDLER_CONSUMED;
}
else
return RX_HANDLER_PASS;
}