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Fixed DHCP packet input filter. Added numerous comments. Code cleanup.

STABLE-2_1_x
likewise 24 years ago
parent
b0c1e37364
commit
8560f6ef2b
1 changed files with 52 additions and 48 deletions
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  1. 100
      src/core/ipv4/ip.c

100
src/core/ipv4/ip.c
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@ -87,7 +87,7 @@ ip_lookup(void *header, struct netif *inp)
iphdr = header;
/* Refuse anything that isn't IPv4. */
/* not IP v4? */
if(IPH_V(iphdr) != 4) {
return 0;
}
@ -137,13 +137,16 @@ struct netif *
ip_route(struct ip_addr *dest)
{
struct netif *netif;
/* iterate through netifs */
for(netif = netif_list; netif != NULL; netif = netif->next) {
/* network mask matches? */
if(ip_addr_maskcmp(dest, &(netif->ip_addr), &(netif->netmask))) {
/* return netif on which to forward IP packet */
return netif;
}
}
/* no matching netif found, use default netif */
return netif_default;
}
#if IP_FORWARD
@ -161,31 +164,29 @@ ip_forward(struct pbuf *p, struct ip_hdr *iphdr, struct netif *inp)
struct netif *netif;
PERF_START;
if((netif = ip_route((struct ip_addr *)&(iphdr->dest))) == NULL) {
/* Find network interface where to forward this IP packet to. */
netif = ip_route((struct ip_addr *)&(iphdr->dest));
if(netif == NULL) {
DEBUGF(IP_DEBUG, ("ip_forward: no forwarding route for 0x%lx found\n",
iphdr->dest.addr));
#if LWIP_SNMP > 0
snmp_inc_ipnoroutes();
#endif
return;
}
/* Don't forward packets onto the same network interface on which
/* Do not forward packets onto the same network interface on which
they arrived. */
if(netif == inp) {
DEBUGF(IP_DEBUG, ("ip_forward: not forward packets back on incoming interface.\n"));
DEBUGF(IP_DEBUG, ("ip_forward: not bouncing packets back on incoming interface.\n"));
#if LWIP_SNMP > 0
snmp_inc_ipnoroutes();
#endif
return;
}
/* Decrement TTL and send ICMP if ttl == 0. */
/* decrement TTL */
IPH_TTL_SET(iphdr, IPH_TTL(iphdr) - 1);
/* send ICMP if TTL == 0 */
if(IPH_TTL(iphdr) == 0) {
/* Don't send ICMP messages in response to ICMP messages */
if(IPH_PROTO(iphdr) != IP_PROTO_ICMP) {
@ -197,7 +198,7 @@ ip_forward(struct pbuf *p, struct ip_hdr *iphdr, struct netif *inp)
return;
}
/* Incremental update of the IP checksum. */
/* Incrementally update the IP checksum. */
if(IPH_CHKSUM(iphdr) >= htons(0xffff - 0x100)) {
IPH_CHKSUM_SET(iphdr, IPH_CHKSUM(iphdr) + htons(0x100) + 1);
} else {
@ -216,7 +217,7 @@ ip_forward(struct pbuf *p, struct ip_hdr *iphdr, struct netif *inp)
#endif
PERF_STOP("ip_forward");
/* transmit pbuf on chosen interface */
netif->output(netif, p, (struct ip_addr *)&(iphdr->dest));
}
#endif /* IP_FORWARD */
@ -236,9 +237,7 @@ err_t
ip_input(struct pbuf *p, struct netif *inp) {
static struct ip_hdr *iphdr;
static struct netif *netif;
static u8_t hl;
static u16_t iphdrlen;
#ifdef IP_STATS
++lwip_stats.ip.recv;
@ -264,12 +263,16 @@ ip_input(struct pbuf *p, struct netif *inp) {
#endif
return ERR_OK;
}
hl = IPH_HL(iphdr);
if(hl * 4 > p->len) {
DEBUGF(IP_DEBUG, ("IP packet dropped due to too short packet %d\n", p->len));
/* obtain IP header length in number of 32-bit words */
iphdrlen = IPH_HL(iphdr);
/* calculate IP header length in bytes */
iphdrlen *= 4;
/* header length exceeds first pbuf length? */
if(iphdrlen > p->len) {
DEBUGF(IP_DEBUG, ("IP header (len %u) does not fit in first pbuf (len %u), IP packet droppped.\n",
iphdrlen, p->len));
/* free (drop) packet pbufs */
pbuf_free(p);
#ifdef IP_STATS
++lwip_stats.ip.lenerr;
@ -282,9 +285,9 @@ ip_input(struct pbuf *p, struct netif *inp) {
}
/* verify checksum */
if(inet_chksum(iphdr, hl * 4) != 0) {
if(inet_chksum(iphdr, iphdrlen) != 0) {
DEBUGF(IP_DEBUG, ("IP packet dropped due to failing checksum 0x%x\n", inet_chksum(iphdr, hl * 4)));
DEBUGF(IP_DEBUG, ("Checksum (0x%x) failed, IP packet dropped.\n", inet_chksum(iphdr, iphdrlen)));
#if IP_DEBUG
ip_debug_print(p);
#endif /* IP_DEBUG */
@ -317,39 +320,42 @@ ip_input(struct pbuf *p, struct netif *inp) {
{
/* unicast to this interface address? */
if(ip_addr_cmp(&(iphdr->dest), &(netif->ip_addr)) ||
/* or broadcast on this interface network address ? */
/* or broadcast matching this interface network address? */
(ip_addr_isbroadcast(&(iphdr->dest), &(netif->netmask)) &&
ip_addr_maskcmp(&(iphdr->dest), &(netif->ip_addr), &(netif->netmask))) ||
/* or restricted broadcast? */
ip_addr_cmp(&(iphdr->dest), IP_ADDR_BROADCAST)) {
DEBUGF(IP_DEBUG, ("ip_input: packet accepted on interface %c%c\n",
netif->name[0], netif->name[1]));
/* break out of for loop */
break;
}
}
}
#if LWIP_DHCP
/* Pass DHCP messages in case of an unconfigured (0.0.0.0) interface, regardless
of destination address. (DHCP replies are sent to the IP address-to-be. This
is according to RFC 1542 section 3.1.1, referred by RFC 2131). */
/* interface unconfigured (0.0.0.0) */
else {
/* remote port is DHCP server? */
if(IPH_PROTO(iphdr) == IP_PROTO_UDP &&
((struct udp_hdr *)((u8_t *)iphdr + IPH_HL(iphdr) * 4))->src == DHCP_SERVER_PORT) {
netif = inp;
/* break out of for loop */
break;
/* Pass DHCP messages regardless of destination address. DHCP traffic is addressed
using link layer addressing (such as Ethernet MAC) so we must not filter on IP.
According to RFC 1542 section 3.1.1, referred by RFC 2131). */
if(netif == NULL) {
/* remote port is DHCP server? */
if(IPH_PROTO(iphdr) == IP_PROTO_UDP) {
DEBUGF(IP_DEBUG, ("ip_input: UDP packet to DHCP client port %u\n",
ntohs(((struct udp_hdr *)((u8_t *)iphdr + iphdrlen))->dest)));
if (ntohs(((struct udp_hdr *)((u8_t *)iphdr + iphdrlen))->dest) == DHCP_CLIENT_PORT) {
DEBUGF(IP_DEBUG, ("ip_input: DHCP packet accepted.\n"));
netif = inp;
}
}
#endif /* LWIP_DHCP */
}
#endif /* LWIP_DHCP */
/* packet not for us? */
if(netif == NULL) {
/* packet not for us, route or discard */
DEBUGF(IP_DEBUG, ("ip_input: packet not for us.\n"));
#if IP_FORWARD
/* non-broadcast packet? */
if(!ip_addr_isbroadcast(&(iphdr->dest), &(inp->netmask))) {
/* try to forward IP packet on (other) interfaces */
ip_forward(p, iphdr, inp);
}
else
@ -374,8 +380,8 @@ ip_input(struct pbuf *p, struct netif *inp) {
#else /* IP_REASSEMBLY */
if((IPH_OFFSET(iphdr) & htons(IP_OFFMASK | IP_MF)) != 0) {
pbuf_free(p);
DEBUGF(IP_DEBUG, ("IP packet dropped since it was fragmented (0x%x).\n",
ntohs(IPH_OFFSET(iphdr))));
DEBUGF(IP_DEBUG, ("IP packet dropped since it was fragmented (0x%x) (while IP_REASSEMBLY == 0).\n",
ntohs(IPH_OFFSET(iphdr))));
#ifdef IP_STATS
++lwip_stats.ip.opterr;
++lwip_stats.ip.drop;
@ -388,9 +394,8 @@ ip_input(struct pbuf *p, struct netif *inp) {
#endif /* IP_REASSEMBLY */
#if IP_OPTIONS == 0
if(hl * 4 > IP_HLEN) {
DEBUGF(IP_DEBUG, ("IP packet dropped since there were IP options.\n"));
if(iphdrlen > IP_HLEN) {
DEBUGF(IP_DEBUG, ("IP packet dropped since there were IP options (while IP_OPTIONS == 0).\n"));
pbuf_free(p);
#ifdef IP_STATS
++lwip_stats.ip.opterr;
@ -403,7 +408,6 @@ ip_input(struct pbuf *p, struct netif *inp) {
}
#endif /* IP_OPTIONS == 0 */
/* send to upper layers */
#if IP_DEBUG
DEBUGF(IP_DEBUG, ("ip_input: \n"));
@ -531,7 +535,7 @@ ip_output_if(struct pbuf *p, struct ip_addr *src, struct ip_addr *dest,
ip_debug_print(p);
#endif /* IP_DEBUG */
DEBUGF(IP_DEBUG, ("netif->output()"));
DEBUGF(IP_DEBUG, ("netif->output()"));
return netif->output(netif, p, dest);
}

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