minix3/commands/dhcpd/ether.c

205 lines
5.6 KiB
C

/* ether.c - Raw Ethernet stuff
* Author: Kees J. Bot
* 16 Dec 2000
*/
#include <sys/types.h>
#include <fcntl.h>
#include <string.h>
#include <sys/asynchio.h>
#include <net/hton.h>
#include <net/gen/in.h>
#include <net/gen/ether.h>
#include <net/gen/eth_hdr.h>
#include <net/gen/ip_hdr.h>
#include <net/gen/icmp.h>
#include <net/gen/icmp_hdr.h>
#include <net/gen/oneCsum.h>
#include <net/gen/udp.h>
#include <net/gen/udp_hdr.h>
#include <net/gen/dhcp.h>
#include "arp.h"
#include "dhcpd.h"
static ether_addr_t BCAST_ETH = {{ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }};
#define BCAST_IP htonl(0xFFFFFFFFUL)
#define LOCALHOST htonl(0x7F000001UL)
static u16_t udp_cksum(ipaddr_t src, ipaddr_t dst, udp_hdr_t *udp)
{
/* Compute the checksum of an UDP packet plus data. */
struct udp_pseudo {
ipaddr_t src, dst;
u8_t zero, proto;
u16_t length;
} pseudo;
size_t len;
/* Fill in the UDP pseudo header that must be prefixed to the UDP
* packet to compute the checksum of the whole thing.
*/
pseudo.src= src;
pseudo.dst= dst;
pseudo.zero= 0;
pseudo.proto= IPPROTO_UDP;
pseudo.length= udp->uh_length;
len= ntohs(udp->uh_length);
if (len & 1) {
/* Length is odd? Pad with a zero. */
B(udp)[len++]= 0;
}
return oneC_sum(oneC_sum(0, &pseudo, sizeof(pseudo)), udp, len);
}
void udp2ether(buf_t *bp, network_t *np)
{
/* Transform a packet in UDP format to raw Ethernet. Ignore the UDP
* addresses, always broadcast from 0.0.0.0.
*/
udp_io_hdr_t udpio;
/* Save the UDP I/O header. */
udpio= *bp->udpio;
/* Fill in the Ethernet, IP and UDP headers. */
bp->eth->eh_dst= BCAST_ETH;
bp->eth->eh_src= np->eth;
bp->eth->eh_proto= htons(ETH_IP_PROTO);
bp->ip->ih_vers_ihl= 0x45;
bp->ip->ih_tos= 0;
bp->ip->ih_length= htons(sizeof(ip_hdr_t)
+ sizeof(udp_hdr_t) + udpio.uih_data_len);
bp->ip->ih_id= 0;
bp->ip->ih_flags_fragoff= ntohs(0x4000);
bp->ip->ih_ttl= IP_MAX_TTL;
bp->ip->ih_proto= IPPROTO_UDP;
bp->ip->ih_hdr_chk= 0;
bp->ip->ih_src= 0;
bp->ip->ih_dst= BCAST_IP;
bp->ip->ih_hdr_chk= ~oneC_sum(0, bp->ip, sizeof(*bp->ip));
bp->udp->uh_src_port= udpio.uih_src_port;
bp->udp->uh_dst_port= udpio.uih_dst_port;
bp->udp->uh_length= htons(sizeof(udp_hdr_t) + udpio.uih_data_len);
bp->udp->uh_chksum= 0;
bp->udp->uh_chksum= ~udp_cksum(bp->ip->ih_src, bp->ip->ih_dst, bp->udp);
}
int ether2udp(buf_t *bp)
{
/* Transform an UDP packet read from raw Ethernet to normal UDP.
* Return true iff the packet is indeed UDP and has no errors.
*/
udp_io_hdr_t udpio;
if (bp->eth->eh_proto != htons(ETH_IP_PROTO)
|| bp->ip->ih_vers_ihl != 0x45
|| bp->ip->ih_proto != IPPROTO_UDP
|| oneC_sum(0, bp->ip, 20) != (u16_t) ~0
|| udp_cksum(bp->ip->ih_src, bp->ip->ih_dst, bp->udp) != (u16_t) ~0
) {
/* Not UDP/IP or checksums bad. */
return 0;
}
udpio.uih_src_addr= bp->ip->ih_src;
udpio.uih_dst_addr= bp->ip->ih_dst;
udpio.uih_src_port= bp->udp->uh_src_port;
udpio.uih_dst_port= bp->udp->uh_dst_port;
udpio.uih_ip_opt_len= 0;
udpio.uih_data_len= ntohs(bp->udp->uh_length) - sizeof(udp_hdr_t);
*bp->udpio= udpio;
return 1;
}
void make_arp(buf_t *bp, network_t *np)
{
/* Create an ARP packet to query for my IP address. */
arp46_t *arp= (arp46_t *) bp->eth;
memset(arp, 0, sizeof(*arp));
arp->dstaddr= BCAST_ETH;
arp->srcaddr= np->eth;
arp->ethtype= htons(ETH_ARP_PROTO);
arp->hdr= htons(ARP_ETHERNET);
arp->pro= htons(ETH_IP_PROTO);
arp->op= htons(ARP_REQUEST);
arp->hln= 6;
arp->pln= 4;
arp->sha= np->eth;
memcpy(arp->spa, &np->ip, sizeof(np->ip));
memcpy(arp->tpa, &np->ip, sizeof(np->ip));
}
int is_arp_me(buf_t *bp, network_t *np)
{
/* True iff an ARP packet is a reply from someone else with an address I
* thought was mine. (That's like, bad.)
*/
arp46_t *arp= (arp46_t *) bp->eth;
if (arp->ethtype == htons(ETH_ARP_PROTO)
&& arp->hdr == htons(ARP_ETHERNET)
&& arp->pro == htons(ETH_IP_PROTO)
&& arp->op == htons(ARP_REPLY)
&& memcmp(&arp->spa, &np->ip, sizeof(np->ip)) == 0
&& memcmp(&arp->sha, &np->eth, sizeof(np->eth)) != 0
) {
np->conflict= arp->sha;
return 1;
}
return 0;
}
void icmp_solicit(buf_t *bp)
{
/* Fill in a router solicitation ICMP packet. */
icmp_hdr_t *icmp= (icmp_hdr_t *) (bp->ip + 1);
bp->ip->ih_vers_ihl= 0x45;
bp->ip->ih_dst= BCAST_IP;
icmp->ih_type= ICMP_TYPE_ROUTE_SOL;
icmp->ih_code= 0;
icmp->ih_hun.ihh_unused= 0;
icmp->ih_chksum= 0;
icmp->ih_chksum= ~oneC_sum(0, icmp, 8);
}
void icmp_advert(buf_t *bp, network_t *np)
{
/* Fill in a router advert to be sent to my own interface. */
icmp_hdr_t *icmp= (icmp_hdr_t *) (bp->ip + 1);
bp->ip->ih_vers_ihl= 0x45;
bp->ip->ih_dst= LOCALHOST;
icmp->ih_type= ICMP_TYPE_ROUTER_ADVER;
icmp->ih_code= 0;
icmp->ih_hun.ihh_ram.iram_na= 1;
icmp->ih_hun.ihh_ram.iram_aes= 2;
icmp->ih_hun.ihh_ram.iram_lt= htons(DELTA_ADV);
((u32_t *) icmp->ih_dun.uhd_data)[0] = np->gateway;
((u32_t *) icmp->ih_dun.uhd_data)[1] = htonl((u32_t) -9999);
icmp->ih_chksum= 0;
icmp->ih_chksum= ~oneC_sum(0, icmp, 16);
}
ipaddr_t icmp_is_advert(buf_t *bp)
{
/* Check if an IP packet is a router advertisement, and if it's genuine,
* i.e. the sender is mentioned in the packet.
*/
icmp_hdr_t *icmp= (icmp_hdr_t *) (bp->ip + 1);
int i;
if (icmp->ih_type == ICMP_TYPE_ROUTER_ADVER) {
for (i= 0; i < icmp->ih_hun.ihh_ram.iram_na; i++) {
if (((u32_t *) icmp->ih_dun.uhd_data)[2*i] == bp->ip->ih_src) {
/* It's a router! */
return bp->ip->ih_src;
}
}
}
return 0;
}