gre: add support for MikroTik Ethernet-over-IP hack.

[tcpdump] / netdissect.c

diff --git a/netdissect.c b/netdissect.c
index 450bb1a25b973847e7726638b95d6b46dffbc19d..000d1ffce8c2c6eb9a47f36e9a79e0b5ec2b258e 100644 (file)
--- a/netdissect.c
+++ b/netdissect.c
@@ -30,6 +30,7 @@
 #include "netdissect.h"
 #include <string.h>
 #include <stdio.h>
+#include <stdlib.h>
 
 #ifdef USE_LIBSMI
 #include <smi.h>
@@ -144,3 +145,157 @@ nd_smi_version_string(void)
        return (NULL);
 #endif
 }
+
+
+int
+nd_push_buffer(netdissect_options *ndo, u_char *new_buffer,
+              const u_char *new_packetp, const u_int newlen)
+{
+       struct netdissect_saved_packet_info *ndspi;
+
+       ndspi = (struct netdissect_saved_packet_info *)malloc(sizeof(struct netdissect_saved_packet_info));
+       if (ndspi == NULL)
+               return (0);     /* fail */
+       ndspi->ndspi_buffer = new_buffer;
+       ndspi->ndspi_packetp = ndo->ndo_packetp;
+       ndspi->ndspi_snapend = ndo->ndo_snapend;
+       ndspi->ndspi_prev = ndo->ndo_packet_info_stack;
+
+       ndo->ndo_packetp = new_packetp;
+       ndo->ndo_snapend = new_packetp + newlen;
+       ndo->ndo_packet_info_stack = ndspi;
+
+       return (1);     /* success */
+}
+
+
+/*
+ * In a given netdissect_options structure:
+ *
+ *    push the current packet information onto the packet information
+ *    stack;
+ *
+ *    given a pointer into the packet and a length past that point in
+ *    the packet, calculate a new snapshot end that's at the lower
+ *    of the current snapshot end and that point in the packet;
+ *
+ *    set the snapshot end to that new value.
+ */
+int
+nd_push_snaplen(netdissect_options *ndo, const u_char *bp, const u_int newlen)
+{
+       struct netdissect_saved_packet_info *ndspi;
+       u_int snaplen_remaining;
+
+       ndspi = (struct netdissect_saved_packet_info *)malloc(sizeof(struct netdissect_saved_packet_info));
+       if (ndspi == NULL)
+               return (0);     /* fail */
+       ndspi->ndspi_buffer = NULL;     /* no new buffer */
+       ndspi->ndspi_packetp = ndo->ndo_packetp;
+       ndspi->ndspi_snapend = ndo->ndo_snapend;
+       ndspi->ndspi_prev = ndo->ndo_packet_info_stack;
+
+       /*
+        * Push the saved previous data onto the stack.
+        */
+       ndo->ndo_packet_info_stack = ndspi;
+
+       /*
+        * Find out how many bytes remain after the current snapend.
+        *
+        * We're restricted to packets with at most UINT_MAX bytes;
+        * cast the result to u_int, so that we don't get truncation
+        * warnings on LP64 and LLP64 platforms.  (ptrdiff_t is
+        * signed and we want an unsigned difference; the pointer
+        * should at most be equal to snapend, and must *never*
+        * be past snapend.)
+        */
+       snaplen_remaining = (u_int)(ndo->ndo_snapend - bp);
+
+       /*
+        * If the new snapend is smaller than the one calculated
+        * above, set the snapend to that value, otherwise leave
+        * it unchanged.
+        */
+       if (newlen <= snaplen_remaining) {
+               /* Snapend isn't past the previous snapend */
+               ndo->ndo_snapend = bp + newlen;
+       }
+
+       return (1);     /* success */
+}
+
+/*
+ * In a given netdissect_options structure:
+ *
+ *    given a pointer into the packet and a length past that point in
+ *    the packet, calculate a new snapshot end that's at the lower
+ *    of the previous snapshot end - or, if there is no previous
+ *    snapshot end, the current snapshot end - and that point in the
+ *    packet;
+ *
+ *    set the snapshot end to that new value.
+ *
+ * This is to change the current snapshot end.  This may increase the
+ * snapshot end, as it may be used, for example, for a Jumbo Payload
+ * option in IPv6.  It must not increase it past the snapshot length
+ * atop which the current one was pushed, however.
+ */
+void
+nd_change_snaplen(netdissect_options *ndo, const u_char *bp, const u_int newlen)
+{
+       struct netdissect_saved_packet_info *ndspi;
+       const u_char *previous_snapend;
+       u_int snaplen_remaining;
+
+       ndspi = ndo->ndo_packet_info_stack;
+       if (ndspi->ndspi_prev != NULL)
+               previous_snapend = ndspi->ndspi_prev->ndspi_snapend;
+       else
+               previous_snapend = ndo->ndo_snapend;
+
+       /*
+        * Find out how many bytes remain after the previous
+        * snapend - or, if there is no previous snapend, after
+        * the current snapend.
+        *
+        * We're restricted to packets with at most UINT_MAX bytes;
+        * cast the result to u_int, so that we don't get truncation
+        * warnings on LP64 and LLP64 platforms.  (ptrdiff_t is
+        * signed and we want an unsigned difference; the pointer
+        * should at most be equal to snapend, and must *never*
+        * be past snapend.)
+        */
+       snaplen_remaining = (u_int)(previous_snapend - bp);
+
+       /*
+        * If the new snapend is smaller than the one calculated
+        * above, set the snapend to that value, otherwise leave
+        * it unchanged.
+        */
+       if (newlen <= snaplen_remaining) {
+               /* Snapend isn't past the previous snapend */
+               ndo->ndo_snapend = bp + newlen;
+       }
+}
+
+void
+nd_pop_packet_info(netdissect_options *ndo)
+{
+       struct netdissect_saved_packet_info *ndspi;
+
+       ndspi = ndo->ndo_packet_info_stack;
+       ndo->ndo_packetp = ndspi->ndspi_packetp;
+       ndo->ndo_snapend = ndspi->ndspi_snapend;
+       ndo->ndo_packet_info_stack = ndspi->ndspi_prev;
+
+       free(ndspi->ndspi_buffer);
+       free(ndspi);
+}
+
+void
+nd_pop_all_packet_info(netdissect_options *ndo)
+{
+       while (ndo->ndo_packet_info_stack != NULL)
+               nd_pop_packet_info(ndo);
+}