*/
/*
- * This is the offset of the beginning of the link-layer header from
- * the beginning of the raw packet data.
+ * The offset of the beginning of the link-layer payload, from the beginning
+ * of the raw packet data, is, in the general case, the sum of a variable
+ * value and a constant value; the variable value may be absent, in which
+ * case the offset is only the constant value, and the constant value may
+ * be zero, in which case the offset is only the variable value.
*
- * It's usually 0, except for 802.11 with a fixed-length radio header.
- * (For 802.11 with a variable-length radio header, we have to generate
- * code to compute that offset; off_linkhdr is 0 in that case.)
- */
-static u_int off_linkhdr;
-
-/*
- * If there's a variable-length header preceding the link-layer header,
- * "reg_off_linkhdr" is the register number for a register containing the
- * length of that header, and therefore the offset of the link-layer
- * header from the beginning of the raw packet data. Otherwise,
- * "reg_off_linkhdr" is -1.
+ * off_linkhdr_constant_part is the constant value.
+ *
+ * reg_off_linkhdr is the register number for a register containing the
+ * variable value, and -1 otherwise.
+ *
+ * off_linkhdr_is_variable is 1 if there's a variable part.
*/
+static u_int off_linkhdr_constant_part;
static int reg_off_linkhdr;
+static int off_linkhdr_is_variable;
/*
* If we're checking a link-layer header for a packet encapsulated in
- * another protocol layer, this is the offset of the previous layers'
- * link-layer header from the beginning of the raw packet data.
+ * another protocol layer, this is the equivalent information for the
+ * previous layers' link-layer header from the beginning of the raw
+ * packet data.
*/
-static u_int off_prevlinkhdr;
+static u_int off_prevlinkhdr_constant_part;
+static int reg_off_prevlinkhdr;
+static int off_prevlinkhdr_is_variable;
/*
- * This is the offset of the outermost layers' link-layer header from
- * the beginning of the raw packet data.
+ * This is the equivalent information for the outermost layers' link-layer
+ * header.
*/
-static u_int off_outermostlinkhdr;
+static u_int off_outermostlinkhdr_constant_part;
+static int reg_off_outermostlinkhdr;
+static int off_outermostlinkhdr_is_variable;
/*
* The offset of the beginning of the link-layer payload, from the beginning
/*
* "off_linktype" is the offset to information in the link-layer header
* giving the packet type. This offset is relative to the beginning
- * of the link-layer header - i.e., it doesn't include off_linkhdr - so
+ * of the link-layer header - i.e., it doesn't include off_linkhdr_constant_part - so
* loads with an offset that includes "off_linktype" should use
* OR_LINKHDR.
*
/*
* These are offsets to the beginning of the network-layer header.
* They are relative to the beginning of the link-layer payload (i.e.,
- * they don't include off_linkhdr or off_linkpl).
+ * they don't include off_linkhdr_constant_part or off_linkpl).
*
* If the link layer never uses 802.2 LLC:
*
init_linktype(p)
pcap_t *p;
{
- outermostlinktype = pcap_datalink(p);
pcap_fddipad = p->fddipad;
+
+ /*
+ * We start out with only one link-layer header.
+ */
+ outermostlinktype = pcap_datalink(p);
+ off_outermostlinkhdr_constant_part = 0;
+ off_outermostlinkhdr_is_variable = 0;
+ reg_off_outermostlinkhdr = -1;
+
prevlinktype = outermostlinktype;
- off_outermostlinkhdr = 0;
+ off_prevlinkhdr_constant_part = 0;
+ off_prevlinkhdr_is_variable = 0;
+ reg_off_prevlinkhdr = -1;
+
+ linktype = outermostlinktype;
+ off_linkhdr_constant_part = 0;
+ off_linkhdr_is_variable = 0;
+ reg_off_linkhdr = -1;
/*
- * No link-layer header inside the payload for another
- * protocol, for now.
+ * XXX
*/
- linktype = prevlinktype;
- off_prevlinkhdr = 0;
+ off_linkpl_constant_part = 0;
+ off_linkpl_is_variable = 0;
+ reg_off_linkpl = -1;
/*
* Assume it's not raw ATM with a pseudo-header, for now.
off_dpc = -1;
off_sls = -1;
- /*
- * Also assume it's not 802.11.
- */
- off_linkhdr = 0;
- off_linkpl_constant_part = 0;
- off_linkpl_is_variable = 0;
-
label_stack_depth = 0;
vlan_stack_depth = 0;
- reg_off_linkhdr = -1;
- reg_off_linkpl = -1;
-
switch (linktype) {
case DLT_ARCNET:
return;
case DLT_NETANALYZER:
- off_linkhdr = 4; /* Ethernet header is past 4-byte pseudo-header */
+ off_linkhdr_constant_part = 4; /* Ethernet header is past 4-byte pseudo-header */
off_linktype = 12;
- off_linkpl_constant_part = off_linkhdr + 14; /* pseudo-header+Ethernet header length */
+ off_linkpl_constant_part = off_linkhdr_constant_part + 14; /* pseudo-header+Ethernet header length */
off_nl = 0; /* Ethernet II */
off_nl_nosnap = 3; /* 802.3+802.2 */
return;
case DLT_NETANALYZER_TRANSPARENT:
- off_linkhdr = 12; /* MAC header is past 4-byte pseudo-header, preamble, and SFD */
+ off_linkhdr_constant_part = 12; /* MAC header is past 4-byte pseudo-header, preamble, and SFD */
off_linktype = 12;
- off_linkpl_constant_part = off_linkhdr + 14; /* pseudo-header+preamble+SFD+Ethernet header length */
+ off_linkpl_constant_part = off_linkhdr_constant_part + 14; /* pseudo-header+preamble+SFD+Ethernet header length */
off_nl = 0; /* Ethernet II */
off_nl_nosnap = 3; /* 802.3+802.2 */
return;
* header.
*
* Otherwise, the length of the prefix preceding the link-layer
- * header is "off_linkhdr".
+ * header is "off_linkhdr_constant_part".
*/
if (s != NULL) {
/*
* do an indirect load, to use the X register as an offset.
*/
s2 = new_stmt(BPF_LD|BPF_IND|size);
- s2->s.k = offset;
+ s2->s.k = off_linkhdr_constant_part + offset;
sappend(s, s2);
} else {
/*
* There is no variable-length header preceding the
- * link-layer header; add in off_linkhdr, which, if there's
- * a fixed-length header preceding the link-layer header,
- * is the length of that header.
+ * link-layer header; add in off_linkhdr_constant_part, which, if
+ * there's a fixed-length header preceding the
+ * link-layer header, is the length of that header.
*/
s = new_stmt(BPF_LD|BPF_ABS|size);
- s->s.k = offset + off_linkhdr;
+ s->s.k = off_linkhdr_constant_part + offset;
}
return s;
}
* header.
*
* Otherwise, the length of the prefix preceding the link-layer
- * header is "off_prevlinkhdr".
+ * header is "off_prevlinkhdr_constant_part".
*/
if (s != NULL) {
/*
* do an indirect load, to use the X register as an offset.
*/
s2 = new_stmt(BPF_LD|BPF_IND|size);
- s2->s.k = offset;
+ s2->s.k = off_prevlinkhdr_constant_part + offset;
sappend(s, s2);
} else {
/*
* There is no variable-length header preceding the
- * link-layer header; add in off_prevlinkhdr, which,
+ * link-layer header; add in off_prevlinkhdr_constant_part, which,
* if there's a fixed-length header preceding the
* link-layer header, is the length of that header.
*/
s = new_stmt(BPF_LD|BPF_ABS|size);
- s->s.k = off_prevlinkhdr + offset;
+ s->s.k = off_prevlinkhdr_constant_part + offset;
}
return s;
}
* header.
*
* Otherwise, the length of the prefix preceding the link-layer
- * header is "off_outermostlinkhdr".
+ * header is "off_outermostlinkhdr_constant_part".
*/
if (s == NULL) {
/*
* Load the length of the fixed-length prefix preceding
* the link-layer header (if any) into the X register,
* and store it in the reg_off_linkpl register.
- * That length is off_outermostlinkhdr.
+ * That length is off_outermostlinkhdr_constant_part.
*/
s = new_stmt(BPF_LDX|BPF_IMM);
- s->s.k = off_outermostlinkhdr;
+ s->s.k = off_outermostlinkhdr_constant_part;
}
/*
return b;
}
+/*
+ * Generate code to load the register containing the variable part of
+ * the offset of the link-layer header into the X register; if no
+ * register for that offset has been allocated, allocate it first.
+ * (The code to set that register will be generated later, but will
+ * be placed earlier in the code sequence.)
+ */
static struct slist *
-gen_prism_llprefixlen(void)
-{
- struct slist *s;
-
- if (reg_off_linkhdr == -1) {
- /*
- * We haven't yet assigned a register for the length
- * of the radio header; allocate one.
- */
- reg_off_linkhdr = alloc_reg();
- }
-
- /*
- * Load the register containing the radio length
- * into the X register.
- */
- s = new_stmt(BPF_LDX|BPF_MEM);
- s->s.k = reg_off_linkhdr;
- return s;
-}
-
-static struct slist *
-gen_avs_llprefixlen(void)
+gen_llprefixlen(void)
{
struct slist *s;
- if (reg_off_linkhdr == -1) {
- /*
- * We haven't yet assigned a register for the length
- * of the AVS header; allocate one.
- */
- reg_off_linkhdr = alloc_reg();
- }
-
- /*
- * Load the register containing the AVS length
- * into the X register.
- */
- s = new_stmt(BPF_LDX|BPF_MEM);
- s->s.k = reg_off_linkhdr;
- return s;
-}
-
-static struct slist *
-gen_radiotap_llprefixlen(void)
-{
- struct slist *s;
+ if (off_linkhdr_is_variable) {
+ if (reg_off_linkhdr == -1) {
+ /*
+ * We haven't yet assigned a register for the
+ * variable part of the offset of the link-layer
+ * header; allocate one.
+ */
+ reg_off_linkhdr = alloc_reg();
+ }
- if (reg_off_linkhdr == -1) {
/*
- * We haven't yet assigned a register for the length
- * of the radiotap header; allocate one.
+ * Load the register containing the variable part of the
+ * offset of the link-layer header into the X register.
*/
- reg_off_linkhdr = alloc_reg();
- }
-
- /*
- * Load the register containing the radiotap length
- * into the X register.
- */
- s = new_stmt(BPF_LDX|BPF_MEM);
- s->s.k = reg_off_linkhdr;
- return s;
-}
-
-/*
- * At the moment we treat PPI as normal Radiotap encoded
- * packets. The difference is in the function that generates
- * the code at the beginning to compute the header length.
- * Since this code generator of PPI supports bare 802.11
- * encapsulation only (i.e. the encapsulated DLT should be
- * DLT_IEEE802_11) we generate code to check for this too.
- */
-static struct slist *
-gen_ppi_llprefixlen(void)
-{
- struct slist *s;
-
- if (reg_off_linkhdr == -1) {
+ s = new_stmt(BPF_LDX|BPF_MEM);
+ s->s.k = reg_off_linkhdr;
+ return s;
+ } else {
/*
- * We haven't yet assigned a register for the length
- * of the radiotap header; allocate one.
+ * That offset isn't variable, there's no variable part,
+ * so we don't need to generate any code.
*/
- reg_off_linkhdr = alloc_reg();
- }
-
- /*
- * Load the register containing the PPI length
- * into the X register.
- */
- s = new_stmt(BPF_LDX|BPF_MEM);
- s->s.k = reg_off_linkhdr;
- return s;
-}
-
-/*
- * Generate code to compute the link-layer header length, if necessary,
- * putting it into the X register, and to return either a pointer to a
- * "struct slist" for the list of statements in that code, or NULL if
- * no code is necessary.
- */
-static struct slist *
-gen_llprefixlen(void)
-{
- switch (linktype) {
-
- case DLT_PRISM_HEADER:
- return gen_prism_llprefixlen();
-
- case DLT_IEEE802_11_RADIO_AVS:
- return gen_avs_llprefixlen();
-
- case DLT_IEEE802_11_RADIO:
- return gen_radiotap_llprefixlen();
-
- case DLT_PPI:
- return gen_ppi_llprefixlen();
-
- default:
return NULL;
}
}
static struct slist *
gen_prevlinkhdrprefixlen(void)
{
- switch (prevlinktype) {
-
- case DLT_PRISM_HEADER:
- return gen_prism_llprefixlen();
-
- case DLT_IEEE802_11_RADIO_AVS:
- return gen_avs_llprefixlen();
-
- case DLT_IEEE802_11_RADIO:
- return gen_radiotap_llprefixlen();
+ struct slist *s;
- case DLT_PPI:
- return gen_ppi_llprefixlen();
+ if (off_prevlinkhdr_is_variable) {
+ if (reg_off_prevlinkhdr == -1) {
+ /*
+ * We haven't yet assigned a register for the
+ * variable part of the offset of the link-layer
+ * header; allocate one.
+ */
+ reg_off_prevlinkhdr = alloc_reg();
+ }
- default:
+ /*
+ * Load the register containing the variable part of the
+ * offset of the link-layer header into the X register.
+ */
+ s = new_stmt(BPF_LDX|BPF_MEM);
+ s->s.k = reg_off_prevlinkhdr;
+ return s;
+ } else {
+ /*
+ * That offset isn't variable, there's no variable part,
+ * so we don't need to generate any code.
+ */
return NULL;
}
}
* into the X register and then added to the index).
*/
tmp = new_stmt(BPF_LD|BPF_IND|size);
- tmp->s.k = off_linkhdr;
+ tmp->s.k = off_linkhdr_constant_part;
sappend(s, tmp);
sappend(inst->s, s);
break;
* link-layer payload, including any 802.2 LLC header, so
* it's 6 bytes past off_nl.
*/
+ prevlinktype = linktype;
+ off_prevlinkhdr_constant_part = off_linkhdr_constant_part;
+ off_prevlinkhdr_is_variable = off_linkhdr_is_variable;
+ reg_off_prevlinkhdr = reg_off_linkhdr;
+
linktype = DLT_PPP;
- off_linkhdr = off_linkpl_constant_part + off_nl + 6; /* 6 bytes past the PPPoE header */
+ off_linkhdr_constant_part = off_linkpl_constant_part + off_nl + 6; /* 6 bytes past the PPPoE header */
+ reg_off_linkhdr = reg_off_linkpl;
+ off_linkhdr_is_variable = off_linkpl_is_variable;
+
off_linktype = 0;
- off_linkpl_constant_part = off_linkhdr + 2;
+ off_linkpl_constant_part = off_linkhdr_constant_part + 2;
+
off_nl = 0;
off_nl_nosnap = 0; /* no 802.2 LLC */
*
* We assume LANE means Ethernet, not Token Ring.
*/
+ prevlinktype = linktype;
+ off_prevlinkhdr_constant_part = off_linkhdr_constant_part;
+ off_prevlinkhdr_is_variable = off_linkhdr_is_variable;
+ reg_off_prevlinkhdr = reg_off_linkhdr;
linktype = DLT_EN10MB;
- off_linkhdr = off_payload + 2; /* Ethernet header */
+ off_linkhdr_constant_part = off_payload + 2; /* Ethernet header */
off_linktype = 12;
- off_linkpl_constant_part = off_linkhdr + 14; /* Ethernet */
+ off_linkpl_constant_part = off_linkhdr_constant_part + 14; /* Ethernet */
off_nl = 0; /* Ethernet II */
off_nl_nosnap = 3; /* 802.3+802.2 */
break;
projects / libpcap / commitdiff
