ip.c File Reference

#include "lwip/opt.h"
#include "lwip/ip.h"
#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/ip_frag.h"
#include "lwip/inet_chksum.h"
#include "lwip/netif.h"
#include "lwip/icmp.h"
#include "lwip/igmp.h"
#include "lwip/raw.h"
#include "lwip/udp.h"
#include "lwip/tcp_impl.h"
#include "lwip/snmp.h"
#include "lwip/dhcp.h"
#include "lwip/autoip.h"
#include "lwip/stats.h"
#include "arch/perf.h"
#include <string.h>

Include dependency graph for ip.c:

Go to the source code of this file.

Macros
#define	LWIP_INLINE_IP_CHKSUM   1
#define	CHECKSUM_GEN_IP_INLINE   0
#define	IP_ACCEPT_LINK_LAYER_ADDRESSING   0

Functions
struct netif *	ip_route (ip_addr_t *dest)
err_t	ip_input (struct pbuf *p, struct netif *inp)
err_t	ip_output_if (struct pbuf *p, ip_addr_t *src, ip_addr_t *dest, u8_t ttl, u8_t tos, u8_t proto, struct netif *netif)
err_t	ip_output (struct pbuf *p, ip_addr_t *src, ip_addr_t *dest, u8_t ttl, u8_t tos, u8_t proto)

Variables
struct netif *	current_netif
const struct ip_hdr *	current_header
ip_addr_t	current_iphdr_src
ip_addr_t	current_iphdr_dest
static u16_t	ip_id

Detailed Description

This is the IPv4 layer implementation for incoming and outgoing IP traffic.

See also

ip_frag.c

Definition in file ip.c.

Macro Definition Documentation

CHECKSUM_GEN_IP_INLINE

#define CHECKSUM_GEN_IP_INLINE   0

Definition at line 69 of file ip.c.

IP_ACCEPT_LINK_LAYER_ADDRESSING

#define IP_ACCEPT_LINK_LAYER_ADDRESSING   0

Definition at line 93 of file ip.c.

LWIP_INLINE_IP_CHKSUM

#define LWIP_INLINE_IP_CHKSUM   1

Set this to 0 in the rare case of wanting to call an extra function to generate the IP checksum (in contrast to calculating it on-the-fly).

Definition at line 64 of file ip.c.

Function Documentation

ip_input()

err_t ip_input	(	struct pbuf *	p,
		struct netif *	inp
	)

This function is called by the network interface device driver when an IP packet is received. The function does the basic checks of the IP header such as packet size being at least larger than the header size etc. If the packet was not destined for us, the packet is forwarded (using ip_forward). The IP checksum is always checked.

Finally, the packet is sent to the upper layer protocol input function.

Parameters

p	the received IP packet (p->payload points to IP header)
inp	the netif on which this packet was received

Returns

ERR_OK if the packet was processed (could return ERR_* if it wasn't processed, but currently always returns ERR_OK)

Definition at line 305 of file ip.c.

{
  struct ip_hdr *iphdr;
  struct netif *netif;
  u16_t iphdr_hlen;
  u16_t iphdr_len;
#if IP_ACCEPT_LINK_LAYER_ADDRESSING
  int check_ip_src=1;
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
 
  IP_STATS_INC(ip.recv);
  snmp_inc_ipinreceives();
 
  /* identify the IP header */
  iphdr = (struct ip_hdr *)p->payload;
  if (IPH_V(iphdr) != 4) {
    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_WARNING, ("IP packet dropped due to bad version number %"U16_F"\n", IPH_V(iphdr)));
    ip_debug_print(p);
    pbuf_free(p);
    IP_STATS_INC(ip.err);
    IP_STATS_INC(ip.drop);
    snmp_inc_ipinhdrerrors();
    return ERR_OK;
  }
 
#ifdef LWIP_HOOK_IP4_INPUT
  if (LWIP_HOOK_IP4_INPUT(p, inp)) {
    /* the packet has been eaten */
    return ERR_OK;
  }
#endif
 
  /* obtain IP header length in number of 32-bit words */
  iphdr_hlen = IPH_HL(iphdr);
  /* calculate IP header length in bytes */
  iphdr_hlen *= 4;
  /* obtain ip length in bytes */
  iphdr_len = ntohs(IPH_LEN(iphdr));
 
  /* header length exceeds first pbuf length, or ip length exceeds total pbuf length? */
  if ((iphdr_hlen > p->len) || (iphdr_len > p->tot_len)) {
    if (iphdr_hlen > p->len) {
      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
        ("IP header (len %"U16_F") does not fit in first pbuf (len %"U16_F"), IP packet dropped.\n",
        iphdr_hlen, p->len));
    }
    if (iphdr_len > p->tot_len) {
      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
        ("IP (len %"U16_F") is longer than pbuf (len %"U16_F"), IP packet dropped.\n",
        iphdr_len, p->tot_len));
    }
    /* free (drop) packet pbufs */
    pbuf_free(p);
    IP_STATS_INC(ip.lenerr);
    IP_STATS_INC(ip.drop);
    snmp_inc_ipindiscards();
    return ERR_OK;
  }
 
  /* verify checksum */
#if CHECKSUM_CHECK_IP
  if (inet_chksum(iphdr, iphdr_hlen) != 0) {
 
    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
      ("Checksum (0x%"X16_F") failed, IP packet dropped.\n", inet_chksum(iphdr, iphdr_hlen)));
    ip_debug_print(p);
    pbuf_free(p);
    IP_STATS_INC(ip.chkerr);
    IP_STATS_INC(ip.drop);
    snmp_inc_ipinhdrerrors();
    return ERR_OK;
  }
#endif
 
  /* Trim pbuf. This should have been done at the netif layer,
   * but we'll do it anyway just to be sure that its done. */
  pbuf_realloc(p, iphdr_len);
 
  /* copy IP addresses to aligned ip_addr_t */
  ip_addr_copy(current_iphdr_dest, iphdr->dest);
  ip_addr_copy(current_iphdr_src, iphdr->src);
 
  /* match packet against an interface, i.e. is this packet for us? */
#if LWIP_IGMP
  if (ip_addr_ismulticast(&current_iphdr_dest)) {
    if ((inp->flags & NETIF_FLAG_IGMP) && (igmp_lookfor_group(inp, &current_iphdr_dest))) {
      netif = inp;
    } else {
      netif = NULL;
    }
  } else
#endif /* LWIP_IGMP */
  {
    /* start trying with inp. if that's not acceptable, start walking the
       list of configured netifs.
       'first' is used as a boolean to mark whether we started walking the list */
    int first = 1;
    netif = inp;
    do {
      LWIP_DEBUGF(IP_DEBUG, ("ip_input: iphdr->dest 0x%"X32_F" netif->ip_addr 0x%"X32_F" (0x%"X32_F", 0x%"X32_F", 0x%"X32_F")\n",
          ip4_addr_get_u32(&iphdr->dest), ip4_addr_get_u32(&netif->ip_addr),
          ip4_addr_get_u32(&iphdr->dest) & ip4_addr_get_u32(&netif->netmask),
          ip4_addr_get_u32(&netif->ip_addr) & ip4_addr_get_u32(&netif->netmask),
          ip4_addr_get_u32(&iphdr->dest) & ~ip4_addr_get_u32(&netif->netmask)));
 
      /* interface is up and configured? */
      if ((netif_is_up(netif)) && (!ip_addr_isany(&(netif->ip_addr)))) {
        /* unicast to this interface address? */
        if (ip_addr_cmp(&current_iphdr_dest, &(netif->ip_addr)) ||
            /* or broadcast on this interface network address? */
            ip_addr_isbroadcast(&current_iphdr_dest, netif)) {
          LWIP_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_AUTOIP
        /* connections to link-local addresses must persist after changing
           the netif's address (RFC3927 ch. 1.9) */
        if ((netif->autoip != NULL) &&
            ip_addr_cmp(&current_iphdr_dest, &(netif->autoip->llipaddr))) {
          LWIP_DEBUGF(IP_DEBUG, ("ip_input: LLA packet accepted on interface %c%c\n",
              netif->name[0], netif->name[1]));
          /* break out of for loop */
          break;
        }
#endif /* LWIP_AUTOIP */
      }
      if (first) {
        first = 0;
        netif = netif_list;
      } else {
        netif = netif->next;
      }
      if (netif == inp) {
        netif = netif->next;
      }
    } while(netif != NULL);
  }
 
#if IP_ACCEPT_LINK_LAYER_ADDRESSING
  /* 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 you want to accept private broadcast communication while a netif is down,
   * define LWIP_IP_ACCEPT_UDP_PORT(dst_port), e.g.:
   *
   * #define LWIP_IP_ACCEPT_UDP_PORT(dst_port) ((dst_port) == PP_NTOHS(12345))
   */
  if (netif == NULL) {
    /* remote port is DHCP server? */
    if (IPH_PROTO(iphdr) == IP_PROTO_UDP) {
      struct udp_hdr *udphdr = (struct udp_hdr *)((u8_t *)iphdr + iphdr_hlen);
      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: UDP packet to DHCP client port %"U16_F"\n",
        ntohs(udphdr->dest)));
      if (IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(udphdr->dest)) {
        LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: DHCP packet accepted.\n"));
        netif = inp;
        check_ip_src = 0;
      }
    }
  }
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
 
  /* broadcast or multicast packet source address? Compliant with RFC 1122: 3.2.1.3 */
#if IP_ACCEPT_LINK_LAYER_ADDRESSING
  /* DHCP servers need 0.0.0.0 to be allowed as source address (RFC 1.1.2.2: 3.2.1.3/a) */
  if (check_ip_src && !ip_addr_isany(&current_iphdr_src))
#endif /* IP_ACCEPT_LINK_LAYER_ADDRESSING */
  {  if ((ip_addr_isbroadcast(&current_iphdr_src, inp)) ||
         (ip_addr_ismulticast(&current_iphdr_src))) {
      /* packet source is not valid */
      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE | LWIP_DBG_LEVEL_WARNING, ("ip_input: packet source is not valid.\n"));
      /* free (drop) packet pbufs */
      pbuf_free(p);
      IP_STATS_INC(ip.drop);
      snmp_inc_ipinaddrerrors();
      snmp_inc_ipindiscards();
      return ERR_OK;
    }
  }
 
  /* packet not for us? */
  if (netif == NULL) {
    /* packet not for us, route or discard */
    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_TRACE, ("ip_input: packet not for us.\n"));
#if IP_FORWARD
    /* non-broadcast packet? */
    if (!ip_addr_isbroadcast(&current_iphdr_dest, inp)) {
      /* try to forward IP packet on (other) interfaces */
      ip_forward(p, iphdr, inp);
    } else
#endif /* IP_FORWARD */
    {
      snmp_inc_ipinaddrerrors();
      snmp_inc_ipindiscards();
    }
    pbuf_free(p);
    return ERR_OK;
  }
  /* packet consists of multiple fragments? */
  if ((IPH_OFFSET(iphdr) & PP_HTONS(IP_OFFMASK | IP_MF)) != 0) {
#if IP_REASSEMBLY /* packet fragment reassembly code present? */
    LWIP_DEBUGF(IP_DEBUG, ("IP packet is a fragment (id=0x%04"X16_F" tot_len=%"U16_F" len=%"U16_F" MF=%"U16_F" offset=%"U16_F"), calling ip_reass()\n",
      ntohs(IPH_ID(iphdr)), p->tot_len, ntohs(IPH_LEN(iphdr)), !!(IPH_OFFSET(iphdr) & PP_HTONS(IP_MF)), (ntohs(IPH_OFFSET(iphdr)) & IP_OFFMASK)*8));
    /* reassemble the packet*/
    p = ip_reass(p);
    /* packet not fully reassembled yet? */
    if (p == NULL) {
      return ERR_OK;
    }
    iphdr = (struct ip_hdr *)p->payload;
#else /* IP_REASSEMBLY == 0, no packet fragment reassembly code present */
    pbuf_free(p);
    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since it was fragmented (0x%"X16_F") (while IP_REASSEMBLY == 0).\n",
      ntohs(IPH_OFFSET(iphdr))));
    IP_STATS_INC(ip.opterr);
    IP_STATS_INC(ip.drop);
    /* unsupported protocol feature */
    snmp_inc_ipinunknownprotos();
    return ERR_OK;
#endif /* IP_REASSEMBLY */
  }
 
#if IP_OPTIONS_ALLOWED == 0 /* no support for IP options in the IP header? */
 
#if LWIP_IGMP
  /* there is an extra "router alert" option in IGMP messages which we allow for but do not police */
  if((iphdr_hlen > IP_HLEN) &&  (IPH_PROTO(iphdr) != IP_PROTO_IGMP)) {
#else
  if (iphdr_hlen > IP_HLEN) {
#endif /* LWIP_IGMP */
    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("IP packet dropped since there were IP options (while IP_OPTIONS_ALLOWED == 0).\n"));
    pbuf_free(p);
    IP_STATS_INC(ip.opterr);
    IP_STATS_INC(ip.drop);
    /* unsupported protocol feature */
    snmp_inc_ipinunknownprotos();
    return ERR_OK;
  }
#endif /* IP_OPTIONS_ALLOWED == 0 */
 
  /* send to upper layers */
  LWIP_DEBUGF(IP_DEBUG, ("ip_input: \n"));
  ip_debug_print(p);
  LWIP_DEBUGF(IP_DEBUG, ("ip_input: p->len %"U16_F" p->tot_len %"U16_F"\n", p->len, p->tot_len));
 
  current_netif = inp;
  current_header = iphdr;
 
#if LWIP_RAW
  /* raw input did not eat the packet? */
  if (raw_input(p, inp) == 0)
#endif /* LWIP_RAW */
  {
    switch (IPH_PROTO(iphdr)) {
#if LWIP_UDP
    case IP_PROTO_UDP:
#if LWIP_UDPLITE
    case IP_PROTO_UDPLITE:
#endif /* LWIP_UDPLITE */
      snmp_inc_ipindelivers();
      udp_input(p, inp);
      break;
#endif /* LWIP_UDP */
#if LWIP_TCP
    case IP_PROTO_TCP:
      snmp_inc_ipindelivers();
      tcp_input(p, inp);
      break;
#endif /* LWIP_TCP */
#if LWIP_ICMP
    case IP_PROTO_ICMP:
      snmp_inc_ipindelivers();
      icmp_input(p, inp);
      break;
#endif /* LWIP_ICMP */
#if LWIP_IGMP
    case IP_PROTO_IGMP:
      igmp_input(p, inp, &current_iphdr_dest);
      break;
#endif /* LWIP_IGMP */
    default:
#if LWIP_ICMP
      /* send ICMP destination protocol unreachable unless is was a broadcast */
      if (!ip_addr_isbroadcast(&current_iphdr_dest, inp) &&
          !ip_addr_ismulticast(&current_iphdr_dest)) {
        p->payload = iphdr;
        icmp_dest_unreach(p, ICMP_DUR_PROTO);
      }
#endif /* LWIP_ICMP */
      pbuf_free(p);
 
      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("Unsupported transport protocol %"U16_F"\n", IPH_PROTO(iphdr)));
 
      IP_STATS_INC(ip.proterr);
      IP_STATS_INC(ip.drop);
      snmp_inc_ipinunknownprotos();
    }
  }
 
  current_netif = NULL;
  current_header = NULL;
  ip_addr_set_any(&current_iphdr_src);
  ip_addr_set_any(&current_iphdr_dest);
 
  return ERR_OK;
}

Referenced by netif_init(), tcpip_input(), and tcpip_thread().

ip_output()

err_t ip_output	(	struct pbuf *	p,
		ip_addr_t *	src,
		ip_addr_t *	dest,
		u8_t	ttl,
		u8_t	tos,
		u8_t	proto
	)

Simple interface to ip_output_if. It finds the outgoing network interface and calls upon ip_output_if to do the actual work.

Parameters

p	the packet to send (p->payload points to the data, e.g. next protocol header; if dest == IP_HDRINCL, p already includes an IP header and p->payload points to that IP header)
src	the source IP address to send from (if src == IP_ADDR_ANY, the IP address of the netif used to send is used as source address)
dest	the destination IP address to send the packet to
ttl	the TTL value to be set in the IP header
tos	the TOS value to be set in the IP header
proto	the PROTOCOL to be set in the IP header

Returns

ERR_RTE if no route is found see ip_output_if() for more return values

Definition at line 818 of file ip.c.

{
  struct netif *netif;
 
  /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
     gets altered as the packet is passed down the stack */
  LWIP_ASSERT("p->ref == 1", p->ref == 1);
 
  if ((netif = ip_route(dest)) == NULL) {
    LWIP_DEBUGF(IP_DEBUG, ("ip_output: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
      ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
    IP_STATS_INC(ip.rterr);
    return ERR_RTE;
  }
 
  return ip_output_if(p, src, dest, ttl, tos, proto, netif);
}

ip_output_if()

err_t ip_output_if	(	struct pbuf *	p,
		ip_addr_t *	src,
		ip_addr_t *	dest,
		u8_t	ttl,
		u8_t	tos,
		u8_t	proto,
		struct netif *	netif
	)

Sends an IP packet on a network interface. This function constructs the IP header and calculates the IP header checksum. If the source IP address is NULL, the IP address of the outgoing network interface is filled in as source address. If the destination IP address is IP_HDRINCL, p is assumed to already include an IP header and p->payload points to it instead of the data.

Parameters

p	the packet to send (p->payload points to the data, e.g. next protocol header; if dest == IP_HDRINCL, p already includes an IP header and p->payload points to that IP header)
src	the source IP address to send from (if src == IP_ADDR_ANY, the IP address of the netif used to send is used as source address)
dest	the destination IP address to send the packet to
ttl	the TTL value to be set in the IP header
tos	the TOS value to be set in the IP header
proto	the PROTOCOL to be set in the IP header
netif	the netif on which to send this packet

Returns

ERR_OK if the packet was sent OK ERR_BUF if p doesn't have enough space for IP/LINK headers returns errors returned by netif->output

Note

ip_id: RFC791 "some host may be able to simply use unique identifiers independent of destination"

Definition at line 641 of file ip.c.

{
#if IP_OPTIONS_SEND
  return ip_output_if_opt(p, src, dest, ttl, tos, proto, netif, NULL, 0);
}
 
err_t ip_output_if_opt(struct pbuf *p, ip_addr_t *src, ip_addr_t *dest,
       u8_t ttl, u8_t tos, u8_t proto, struct netif *netif, void *ip_options,
       u16_t optlen)
{
#endif /* IP_OPTIONS_SEND */
  struct ip_hdr *iphdr;
  ip_addr_t dest_addr;
#if CHECKSUM_GEN_IP_INLINE
  u32_t chk_sum = 0;
#endif /* CHECKSUM_GEN_IP_INLINE */
 
  /* pbufs passed to IP must have a ref-count of 1 as their payload pointer
     gets altered as the packet is passed down the stack */
  LWIP_ASSERT("p->ref == 1", p->ref == 1);
 
  snmp_inc_ipoutrequests();
 
  /* Should the IP header be generated or is it already included in p? */
  if (dest != IP_HDRINCL) {
    u16_t ip_hlen = IP_HLEN;
#if IP_OPTIONS_SEND
    u16_t optlen_aligned = 0;
    if (optlen != 0) {
#if CHECKSUM_GEN_IP_INLINE
      int i;
#endif /* CHECKSUM_GEN_IP_INLINE */
      /* round up to a multiple of 4 */
      optlen_aligned = ((optlen + 3) & ~3);
      ip_hlen += optlen_aligned;
      /* First write in the IP options */
      if (pbuf_header(p, optlen_aligned)) {
        LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_output_if_opt: not enough room for IP options in pbuf\n"));
        IP_STATS_INC(ip.err);
        snmp_inc_ipoutdiscards();
        return ERR_BUF;
      }
      MEMCPY(p->payload, ip_options, optlen);
      if (optlen < optlen_aligned) {
        /* zero the remaining bytes */
        memset(((char*)p->payload) + optlen, 0, optlen_aligned - optlen);
      }
#if CHECKSUM_GEN_IP_INLINE
      for (i = 0; i < optlen_aligned/2; i++) {
        chk_sum += ((u16_t*)p->payload)[i];
      }
#endif /* CHECKSUM_GEN_IP_INLINE */
    }
#endif /* IP_OPTIONS_SEND */
    /* generate IP header */
    if (pbuf_header(p, IP_HLEN)) {
      LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_output: not enough room for IP header in pbuf\n"));
 
      IP_STATS_INC(ip.err);
      snmp_inc_ipoutdiscards();
      return ERR_BUF;
    }
 
    iphdr = (struct ip_hdr *)p->payload;
    LWIP_ASSERT("check that first pbuf can hold struct ip_hdr",
               (p->len >= sizeof(struct ip_hdr)));
 
    IPH_TTL_SET(iphdr, ttl);
    IPH_PROTO_SET(iphdr, proto);
#if CHECKSUM_GEN_IP_INLINE
    chk_sum += LWIP_MAKE_U16(proto, ttl);
#endif /* CHECKSUM_GEN_IP_INLINE */
 
    /* dest cannot be NULL here */
    ip_addr_copy(iphdr->dest, *dest);
#if CHECKSUM_GEN_IP_INLINE
    chk_sum += ip4_addr_get_u32(&iphdr->dest) & 0xFFFF;
    chk_sum += ip4_addr_get_u32(&iphdr->dest) >> 16;
#endif /* CHECKSUM_GEN_IP_INLINE */
 
    IPH_VHL_SET(iphdr, 4, ip_hlen / 4);
    IPH_TOS_SET(iphdr, tos);
#if CHECKSUM_GEN_IP_INLINE
    chk_sum += LWIP_MAKE_U16(tos, iphdr->_v_hl);
#endif /* CHECKSUM_GEN_IP_INLINE */
    IPH_LEN_SET(iphdr, htons(p->tot_len));
#if CHECKSUM_GEN_IP_INLINE
    chk_sum += iphdr->_len;
#endif /* CHECKSUM_GEN_IP_INLINE */
    IPH_OFFSET_SET(iphdr, 0);
    IPH_ID_SET(iphdr, htons(ip_id));
#if CHECKSUM_GEN_IP_INLINE
    chk_sum += iphdr->_id;
#endif /* CHECKSUM_GEN_IP_INLINE */
    ++ip_id;
 
    if (ip_addr_isany(src)) {
      ip_addr_copy(iphdr->src, netif->ip_addr);
    } else {
      /* src cannot be NULL here */
      ip_addr_copy(iphdr->src, *src);
    }
 
#if CHECKSUM_GEN_IP_INLINE
    chk_sum += ip4_addr_get_u32(&iphdr->src) & 0xFFFF;
    chk_sum += ip4_addr_get_u32(&iphdr->src) >> 16;
    chk_sum = (chk_sum >> 16) + (chk_sum & 0xFFFF);
    chk_sum = (chk_sum >> 16) + chk_sum;
    chk_sum = ~chk_sum;
    iphdr->_chksum = chk_sum; /* network order */
#else /* CHECKSUM_GEN_IP_INLINE */
    IPH_CHKSUM_SET(iphdr, 0);
#if CHECKSUM_GEN_IP
    IPH_CHKSUM_SET(iphdr, inet_chksum(iphdr, ip_hlen));
#endif
#endif /* CHECKSUM_GEN_IP_INLINE */
  } else {
    /* IP header already included in p */
    iphdr = (struct ip_hdr *)p->payload;
    ip_addr_copy(dest_addr, iphdr->dest);
    dest = &dest_addr;
  }
 
  IP_STATS_INC(ip.xmit);
 
  LWIP_DEBUGF(IP_DEBUG, ("ip_output_if: %c%c%"U16_F"\n", netif->name[0], netif->name[1], netif->num));
  ip_debug_print(p);
 
#if ENABLE_LOOPBACK
  if (ip_addr_cmp(dest, &netif->ip_addr)) {
    /* Packet to self, enqueue it for loopback */
    LWIP_DEBUGF(IP_DEBUG, ("netif_loop_output()"));
    return netif_loop_output(netif, p, dest);
  }
#if LWIP_IGMP
  if ((p->flags & PBUF_FLAG_MCASTLOOP) != 0) {
    netif_loop_output(netif, p, dest);
  }
#endif /* LWIP_IGMP */
#endif /* ENABLE_LOOPBACK */
#if IP_FRAG
  /* don't fragment if interface has mtu set to 0 [loopif] */
  if (netif->mtu && (p->tot_len > netif->mtu)) {
    return ip_frag(p, netif, dest);
  }
#endif /* IP_FRAG */
 
  LWIP_DEBUGF(IP_DEBUG, ("netif->output()"));
  return netif->output(netif, p, dest);
}

Referenced by ip_output().

ip_route()

struct netif * ip_route

(

ip_addr_t *

dest

)

Finds the appropriate network interface for a given IP address. It searches the list of network interfaces linearly. A match is found if the masked IP address of the network interface equals the masked IP address given to the function.

Parameters

dest	the destination IP address for which to find the route

Returns

the netif on which to send to reach dest

Definition at line 124 of file ip.c.

{
  struct netif *netif;
 
#ifdef LWIP_HOOK_IP4_ROUTE
  netif = LWIP_HOOK_IP4_ROUTE(dest);
  if (netif != NULL) {
    return netif;
  }
#endif
 
  /* iterate through netifs */
  for (netif = netif_list; netif != NULL; netif = netif->next) {
    /* network mask matches? */
    if (netif_is_up(netif)) {
      if (ip_addr_netcmp(dest, &(netif->ip_addr), &(netif->netmask))) {
        /* return netif on which to forward IP packet */
        return netif;
      }
    }
  }
  if ((netif_default == NULL) || (!netif_is_up(netif_default))) {
    LWIP_DEBUGF(IP_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("ip_route: No route to %"U16_F".%"U16_F".%"U16_F".%"U16_F"\n",
      ip4_addr1_16(dest), ip4_addr2_16(dest), ip4_addr3_16(dest), ip4_addr4_16(dest)));
    IP_STATS_INC(ip.rterr);
    snmp_inc_ipoutnoroutes();
    return NULL;
  }
  /* no matching netif found, use default netif */
  return netif_default;
}

Referenced by ip_output().

Variable Documentation

current_header

const struct ip_hdr* current_header

Header of the input packet currently being processed.

Definition at line 105 of file ip.c.

Referenced by ip_input().

current_iphdr_dest

ip_addr_t current_iphdr_dest

Destination IP address of current_header

Definition at line 109 of file ip.c.

Referenced by ip_input().

current_iphdr_src

ip_addr_t current_iphdr_src

Source IP address of current_header

Definition at line 107 of file ip.c.

Referenced by ip_input().

current_netif

struct netif* current_netif

The interface that provided the packet for the current callback invocation.

Definition at line 100 of file ip.c.

Referenced by ip_input().

ip_id

u16_t ip_id

static

The IP header ID of the next outgoing IP packet

Definition at line 112 of file ip.c.