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| author | Guy Harris <guy@alum.mit.edu> | 2010-02-21 00:27:00 -0800 |
|---|---|---|
| committer | Guy Harris <guy@alum.mit.edu> | 2010-02-21 00:27:00 -0800 |
| commit | e8b523758959c1854689d71c7a4686c631e5501c (patch) | |
| tree | 67d50632c8f8f0410d2a8d227a78709a7aca1ca2 /print-ether.c | |
| parent | b00042a8ae3656f01e022bf6df1eb761e6323d3d (diff) | |
| download | tcpdump-e8b523758959c1854689d71c7a4686c631e5501c.tar.gz | |
Don't directly fetch multi-byte integers from packets.
Use the EXTRACT_ macros to extract multi-byte integral values from
packets, rather than just dereferencing pointers into the packet; there
is no guarantee that the packet data will be aligned on the right
boundary, and there is no guarantee that, if they're not, a direct
access will work correctly.
Diffstat (limited to 'print-ether.c')
| -rw-r--r-- | print-ether.c | 33 |
1 files changed, 20 insertions, 13 deletions
diff --git a/print-ether.c b/print-ether.c index 20a2a65f..581d6882 100644 --- a/print-ether.c +++ b/print-ether.c @@ -33,6 +33,7 @@ static const char rcsid[] _U_ = #include <pcap.h> #include "interface.h" +#include "extract.h" #include "addrtoname.h" #include "ethertype.h" @@ -86,24 +87,27 @@ static inline void ether_hdr_print(register const u_char *bp, u_int length) { register const struct ether_header *ep; + u_int16_t ether_type; + ep = (const struct ether_header *)bp; (void)printf("%s > %s", etheraddr_string(ESRC(ep)), etheraddr_string(EDST(ep))); + ether_type = EXTRACT_16BITS(&ep->ether_type); if (!qflag) { - if (ntohs(ep->ether_type) <= ETHERMTU) + if (ether_type <= ETHERMTU) (void)printf(", 802.3"); else (void)printf(", ethertype %s (0x%04x)", - tok2str(ethertype_values,"Unknown", ntohs(ep->ether_type)), - ntohs(ep->ether_type)); + tok2str(ethertype_values,"Unknown", ether_type), + ether_type); } else { - if (ntohs(ep->ether_type) <= ETHERMTU) + if (ether_type <= ETHERMTU) (void)printf(", 802.3"); else - (void)printf(", %s", tok2str(ethertype_values,"Unknown Ethertype (0x%04x)", ntohs(ep->ether_type))); + (void)printf(", %s", tok2str(ethertype_values,"Unknown Ethertype (0x%04x)", ether_type)); } (void)printf(", length %u: ", length); @@ -129,7 +133,7 @@ ether_print(const u_char *p, u_int length, u_int caplen) ep = (struct ether_header *)p; p += ETHER_HDRLEN; - ether_type = ntohs(ep->ether_type); + ether_type = EXTRACT_16BITS(&ep->ether_type); /* * Is it (gag) an 802.3 encapsulation? @@ -226,13 +230,16 @@ ether_encap_print(u_short ether_type, const u_char *p, return (1); case ETHERTYPE_8021Q: - if (eflag) - printf("vlan %u, p %u%s, ", - ntohs(*(u_int16_t *)p) & 0xfff, - ntohs(*(u_int16_t *)p) >> 13, - (ntohs(*(u_int16_t *)p) & 0x1000) ? ", CFI" : ""); + if (eflag) { + u_int16_t tag = EXTRACT_16BITS(p); + + printf("vlan %u, p %u%s, ", + tag & 0xfff, + tag >> 13, + (tag & 0x1000) ? ", CFI" : ""); + } - ether_type = ntohs(*(u_int16_t *)(p + 2)); + ether_type = EXTRACT_16BITS(p + 2); p += 4; length -= 4; caplen -= 4; @@ -259,7 +266,7 @@ ether_encap_print(u_short ether_type, const u_char *p, return (1); case ETHERTYPE_JUMBO: - ether_type = ntohs(*(u_int16_t *)(p)); + ether_type = EXTRACT_16BITS(p); p += 2; length -= 2; caplen -= 2; |