Shrinked ICMP code, added option to NOT check icoming ECHO pbuf for size (just use it): LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN

CHANGELOG

@@ -19,6 +19,10 @@ HISTORY
 
   ++ New features:
 
+  2009-05-09 Simon Goldschmidt
+  * icmp.h, icmp.c: Shrinked ICMP code, added option to NOT check icoming
+    ECHO pbuf for size (just use it): LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
+
   2009-05-05 Simon Goldschmidt, Jakob Stoklund Olesen
   * ip.h, ip.c: Added ip_current_netif() & ip_current_header() to receive
     extended info about the currently received packet.

src/core/ipv4/icmp.c

@@ -53,9 +53,18 @@
 
 #include <string.h>
 
+/** Small optimization: set to 0 if incoming PBUF_POOL pbuf always can be
+ * used to modify and send a response packet (and to 1 if this is not the case,
+ * e.g. when link header is stripped of when receiving) */
+#ifndef LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
+#define LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN 1
+#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
+
 /* The amount of data from the original packet to return in a dest-unreachable */
 #define ICMP_DEST_UNREACH_DATASIZE 8
 
+static void icmp_send_response(struct pbuf *p, u8_t type, u8_t code);
+
 /**
  * Processes ICMP input packets, called from ip_input().
  *
@@ -130,6 +139,7 @@ icmp_input(struct pbuf *p, struct netif *inp)
       snmp_inc_icmpinerrors();
       return;
     }
+#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
     if (pbuf_header(p, (PBUF_IP_HLEN + PBUF_LINK_HLEN))) {
       /* p is not big enough to contain link headers
        * allocate a new one and copy p into it
@@ -170,6 +180,7 @@ icmp_input(struct pbuf *p, struct netif *inp)
         goto memerr;
       }
     }
+#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
     /* At this point, all checks are OK. */
     /* We generate an answer by switching the dest and src ip addresses,
      * setting the icmp type to ECHO_RESPONSE and updating the checksum. */
@@ -222,11 +233,13 @@ lenerr:
   ICMP_STATS_INC(icmp.lenerr);
   snmp_inc_icmpinerrors();
   return;
+#if LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN
 memerr:
   pbuf_free(p);
   ICMP_STATS_INC(icmp.err);
   snmp_inc_icmpinerrors();
   return;
+#endif /* LWIP_ICMP_ECHO_CHECK_INPUT_PBUF_LEN */
 }
 
 /**
@@ -241,40 +254,7 @@ memerr:
 void
 icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
 {
-  struct pbuf *q;
+  icmp_send_response(p, ICMP_DUR, t);
-  struct ip_hdr *iphdr;
-  struct icmp_dur_hdr *idur;
-
-  /* ICMP header + IP header + 8 bytes of data */
-  q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
-                 PBUF_RAM);
-  if (q == NULL) {
-    LWIP_DEBUGF(ICMP_DEBUG, ("icmp_dest_unreach: failed to allocate pbuf for ICMP packet.\n"));
-    return;
-  }
-  LWIP_ASSERT("check that first pbuf can hold icmp message",
-             (q->len >= (sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
-
-  iphdr = p->payload;
-
-  idur = q->payload;
-  ICMPH_TYPE_SET(idur, ICMP_DUR);
-  ICMPH_CODE_SET(idur, t);
-
-  SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_dur_hdr), p->payload,
-          IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
-
-  /* calculate checksum */
-  idur->chksum = 0;
-  idur->chksum = inet_chksum(idur, q->len);
-  ICMP_STATS_INC(icmp.xmit);
-  /* increase number of messages attempted to send */
-  snmp_inc_icmpoutmsgs();
-  /* increase number of destination unreachable messages attempted to send */
-  snmp_inc_icmpoutdestunreachs();
-
-  ip_output(q, NULL, &(iphdr->src), ICMP_TTL, 0, IP_PROTO_ICMP);
-  pbuf_free(q);
 }
 
 #if IP_FORWARD || IP_REASSEMBLY
@@ -287,20 +267,37 @@ icmp_dest_unreach(struct pbuf *p, enum icmp_dur_type t)
  */
 void
 icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
+{
+  icmp_send_response(p, ICMP_TE, t);
+}
+
+#endif /* IP_FORWARD || IP_REASSEMBLY */
+
+/**
+ * Send an icmp packet in response to an incoming packet.
+ *
+ * @param p the input packet for which the 'unreachable' should be sent,
+ *          p->payload pointing to the IP header
+ * @param type Type of the ICMP header
+ * @param code Code of the ICMP header
+ */
+static void
+icmp_send_response(struct pbuf *p, u8_t type, u8_t code)
 {
   struct pbuf *q;
   struct ip_hdr *iphdr;
-  struct icmp_te_hdr *tehdr;
+  /* we can use the echo header here */
+  struct icmp_echo_hdr *icmphdr;
 
   /* ICMP header + IP header + 8 bytes of data */
-  q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
+  q = pbuf_alloc(PBUF_IP, sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE,
                  PBUF_RAM);
   if (q == NULL) {
     LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded: failed to allocate pbuf for ICMP packet.\n"));
     return;
   }
   LWIP_ASSERT("check that first pbuf can hold icmp message",
-             (q->len >= (sizeof(struct icmp_dur_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
+             (q->len >= (sizeof(struct icmp_echo_hdr) + IP_HLEN + ICMP_DEST_UNREACH_DATASIZE)));
 
   iphdr = p->payload;
   LWIP_DEBUGF(ICMP_DEBUG, ("icmp_time_exceeded from "));
@@ -309,17 +306,19 @@ icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
   ip_addr_debug_print(ICMP_DEBUG, &(iphdr->dest));
   LWIP_DEBUGF(ICMP_DEBUG, ("\n"));
 
-  tehdr = q->payload;
+  icmphdr = q->payload;
-  ICMPH_TYPE_SET(tehdr, ICMP_TE);
+  icmphdr->type = type;
-  ICMPH_CODE_SET(tehdr, t);
+  icmphdr->code = code;
+  icmphdr->id = 0;
+  icmphdr->seqno = 0;
 
   /* copy fields from original packet */
-  SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_dur_hdr), (u8_t *)p->payload,
+  SMEMCPY((u8_t *)q->payload + sizeof(struct icmp_echo_hdr), (u8_t *)p->payload,
           IP_HLEN + ICMP_DEST_UNREACH_DATASIZE);
 
   /* calculate checksum */
-  tehdr->chksum = 0;
+  icmphdr->chksum = 0;
-  tehdr->chksum = inet_chksum(tehdr, q->len);
+  icmphdr->chksum = inet_chksum(icmphdr, q->len);
   ICMP_STATS_INC(icmp.xmit);
   /* increase number of messages attempted to send */
   snmp_inc_icmpoutmsgs();
@@ -329,6 +328,4 @@ icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t)
   pbuf_free(q);
 }
 
-#endif /* IP_FORWARD */
-
 #endif /* LWIP_ICMP */

src/include/ipv4/lwip/icmp.h

@@ -78,39 +78,30 @@ void icmp_time_exceeded(struct pbuf *p, enum icmp_te_type t);
 #ifdef PACK_STRUCT_USE_INCLUDES
 #  include "arch/bpstruct.h"
 #endif
+/** This is the standard ICMP header only that the u32_t data
+ *  is splitted to two u16_t like ICMP echo needs it.
+ *  This header is also used for other ICMP types that do not
+ *  use the data part.
+ */
 PACK_STRUCT_BEGIN
 struct icmp_echo_hdr {
-  PACK_STRUCT_FIELD(u16_t _type_code);
+  PACK_STRUCT_FIELD(u8_t type);
+  PACK_STRUCT_FIELD(u8_t code);
   PACK_STRUCT_FIELD(u16_t chksum);
   PACK_STRUCT_FIELD(u16_t id);
   PACK_STRUCT_FIELD(u16_t seqno);
 } PACK_STRUCT_STRUCT;
 PACK_STRUCT_END
-
-PACK_STRUCT_BEGIN
-struct icmp_dur_hdr {
-  PACK_STRUCT_FIELD(u16_t _type_code);
-  PACK_STRUCT_FIELD(u16_t chksum);
-  PACK_STRUCT_FIELD(u32_t unused);
-} PACK_STRUCT_STRUCT;
-PACK_STRUCT_END
-
-PACK_STRUCT_BEGIN
-struct icmp_te_hdr {
-  PACK_STRUCT_FIELD(u16_t _type_code);
-  PACK_STRUCT_FIELD(u16_t chksum);
-  PACK_STRUCT_FIELD(u32_t unused);
-} PACK_STRUCT_STRUCT;
-PACK_STRUCT_END
 #ifdef PACK_STRUCT_USE_INCLUDES
 #  include "arch/epstruct.h"
 #endif
 
-#define ICMPH_TYPE(hdr) (ntohs((hdr)->_type_code) >> 8)
+#define ICMPH_TYPE(hdr) ((hdr)->type)
-#define ICMPH_CODE(hdr) (ntohs((hdr)->_type_code) & 0xff)
+#define ICMPH_CODE(hdr) ((hdr)->code)
 
-#define ICMPH_TYPE_SET(hdr, type) ((hdr)->_type_code = htons(ICMPH_CODE(hdr) | ((type) << 8)))
+/** Combines type and code to an u16_t */
-#define ICMPH_CODE_SET(hdr, code) ((hdr)->_type_code = htons((code) | (ICMPH_TYPE(hdr) << 8)))
+#define ICMPH_TYPE_SET(hdr, t) ((hdr)->type = (t))
+#define ICMPH_CODE_SET(hdr, c) ((hdr)->code = (c))
 
 #ifdef __cplusplus
 }