struct udpiphdr *udp_read(void)
{
int len;
char *ptr;
struct ether_header *eptr;
for ( ; ; ) {
// 从分组捕获设备获取下一个分组
ptr = next_pcap(&len);
switch (datalink) {
case DLT_NULL: // loopback header = 4 bytes
return(udp_check(ptr + 4, len - 4));
case DLT_EN10MB:
eptr = (struct ether_header *) ptr;
if (ntohs(eptr->ether_type) != ETHERTYPE_IP) {
err_quit("Ethernet type %x not IP", ntohs(eptr->ether_type));
}
return(udp_check(ptr + 14, len - 14));
case DLT_SLIP: // SLIP header = 24 bytes
return(udp_check(ptr + 24, len - 24));
case DLT_PPP: // PPP header = 24 bytes
return(udp_check(ptr + 24, len - 24));
default:
err_quit("unsupported datalink (%d)", datalink);
}
}
}
// This is a very weird function, look at udpCheckReceiveFork() in matlab.c for the "why"
int udpmsg_receive(udpmsg *packet)
{
char recv_buf[MAXMSGLENGTH+10];
char senderIP[16]; // "xxx.xxx.xxx.xxx\0"
int ret = 0;
if(udp_check(0)) {
udp_read(recv_buf, sizeof(recv_buf), senderIP);
// printf("%s\n", senderIP);
// First if clause determines whether message is from Psychtoolbox
if (!strcmp(senderIP, macIP)) {
if(strlen(recv_buf)>10 && recv_buf[9]==' ' && strcmp(recv_buf,last_recv)!=0) {
strcpy(last_recv, recv_buf);
strncpy(packet->id, recv_buf, 9);
packet->id[9] = 0;
strcpy(packet->msg, recv_buf+10);
if (strcmp(packet->msg,"RECEIVED")==0)
packet->received = 1;
else if (strcmp(packet->msg,"EXECUTED")==0)
packet->executed = 1;
else {
/* if it is a new message confirm its receipt */
strcpy(recv_buf+10, "RECEIVED");
udp_send(recv_buf, macIP);
}
ret = 1;
}
}
}
return ret;
}
int udp_send(struct netdev *nd, struct sin *from, struct sin *to, struct buflist *data)
{
struct buflist bl, *blp;
struct udphdr udp;
int size = 0;
bl.data = &udp;
bl.size = sizeof(udp);
bl.next = data;
for (blp = &bl; blp; blp = blp->next)
size += blp->size;
udp.udp_source = from->sin_port;
udp.udp_dest = to->sin_port;
udp.udp_length = htons(size);
udp.udp_check = 0;
udp.udp_check = udp_check(&udp, from, to, &bl, size);
return ip_send(nd, 0x11, from->sin_addr, to->sin_addr, &bl);
}
int udp_rcv(struct sk_buff *skb, struct device *dev, struct options *opt,
__u32 daddr, unsigned short len,
__u32 saddr, int redo, struct inet_protocol *protocol)
{
struct sock *sk;
struct udphdr *uh;
unsigned short ulen;
int addr_type;
/*
* If we're doing a "redo" (the socket was busy last time
* around), we can just queue the packet now..
*/
if (redo) {
udp_queue_rcv_skb(skb->sk, skb);
return 0;
}
/*
* First time through the loop.. Do all the setup stuff
* (including finding out the socket we go to etc)
*/
addr_type = IS_MYADDR;
if(!dev || dev->pa_addr!=daddr)
addr_type=ip_chk_addr(daddr);
/*
* Get the header.
*/
uh = (struct udphdr *) skb->h.uh;
ip_statistics.IpInDelivers++;
/*
* Validate the packet and the UDP length.
*/
ulen = ntohs(uh->len);
if (ulen > len || len < sizeof(*uh) || ulen < sizeof(*uh))
{
NETDEBUG(printk("UDP: short packet: %d/%d\n", ulen, len));
udp_statistics.UdpInErrors++;
kfree_skb(skb, FREE_WRITE);
return(0);
}
/* RFC1122 warning: According to 4.1.3.6, we MUST discard any */
/* datagram which has an invalid source address, either here or */
/* in IP. */
/* Right now, IP isn't doing it, and neither is UDP. It's on the */
/* FIXME list for IP, though, so I wouldn't worry about it. */
/* (That's the Right Place to do it, IMHO.) -- MS */
if (uh->check && (
( (skb->ip_summed == CHECKSUM_HW) && udp_check(uh, len, saddr, daddr, skb->csum ) ) ||
( (skb->ip_summed == CHECKSUM_NONE) && udp_check(uh, len, saddr, daddr,csum_partial((char*)uh, len, 0)))
/* skip if CHECKSUM_UNNECESSARY */
)
)
{
/* <*****@*****.**> wants to know, who sent it, to
go and stomp on the garbage sender... */
/* RFC1122: OK. Discards the bad packet silently (as far as */
/* the network is concerned, anyway) as per 4.1.3.4 (MUST). */
NETDEBUG(printk("UDP: bad checksum. From %08lX:%d to %08lX:%d ulen %d\n",
ntohl(saddr),ntohs(uh->source),
ntohl(daddr),ntohs(uh->dest),
ulen));
udp_statistics.UdpInErrors++;
kfree_skb(skb, FREE_WRITE);
return(0);
}
/*
* These are supposed to be switched.
*/
skb->daddr = saddr;
skb->saddr = daddr;
len=ulen;
skb->dev = dev;
skb_trim(skb,len);
#ifdef CONFIG_IP_MULTICAST
if (addr_type==IS_BROADCAST || addr_type==IS_MULTICAST)
return udp_v4_mcast_deliver(skb, uh, saddr, daddr);
#endif
#ifdef CONFIG_IP_TRANSPARENT_PROXY
if(skb->redirport)
sk = udp_v4_proxy_lookup(saddr, uh->source, daddr, uh->dest,
dev->pa_addr, skb->redirport, dev);
else
#endif
sk = udp_v4_lookup(saddr, uh->source, daddr, uh->dest, dev);
if (sk == NULL)
{
udp_statistics.UdpNoPorts++;
if (addr_type != IS_BROADCAST && addr_type != IS_MULTICAST)
{
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0, dev);
}
/*
* Hmm. We got an UDP broadcast to a port to which we
* don't wanna listen. Ignore it.
*/
skb->sk = NULL;
kfree_skb(skb, FREE_WRITE);
return(0);
}
udp_deliver(sk, skb);
return 0;
}
