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Fix "pppoes" filter for links with variable-length prefix to link header #835

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Fix "pppoes" filter for links with variable-length prefix to link header #835

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d605210
compiler_state: redefine off_outermostlinkhdr as pointer to off_*linkhdr
aliemjay Aug 14, 2019
0477aa8
fix "pppoes" filter for IEE_802_11* link types!
aliemjay Aug 14, 2019
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49 changes: 20 additions & 29 deletions gencode.c
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Original file line number Diff line number Diff line change
Expand Up @@ -172,6 +172,7 @@ struct addrinfo {
{ \
(cs)->prevlinktype = (cs)->linktype; \
(cs)->off_prevlinkhdr = (cs)->off_linkhdr; \
(cs)->off_outermostlinkhdr = &((cs)->off_prevlinkhdr); \
(cs)->linktype = (new_linktype); \
(cs)->off_linkhdr.is_variable = (new_is_variable); \
(cs)->off_linkhdr.constant_part = (new_constant_part); \
Expand Down Expand Up @@ -302,10 +303,9 @@ struct _compiler_state {
bpf_abs_offset off_prevlinkhdr;

/*
* This is the equivalent information for the outermost layers'
* link-layer header.
* This is a pointer to either off_linkhdr of off_prevlinkhdr.
*/
bpf_abs_offset off_outermostlinkhdr;
bpf_abs_offset *off_outermostlinkhdr;

/*
* Absolute offset of the beginning of the link-layer payload.
Expand Down Expand Up @@ -1140,14 +1140,7 @@ init_linktype(compiler_state_t *cstate, pcap_t *p)
* We start out with only one link-layer header.
*/
cstate->outermostlinktype = pcap_datalink(p);
cstate->off_outermostlinkhdr.constant_part = 0;
cstate->off_outermostlinkhdr.is_variable = 0;
cstate->off_outermostlinkhdr.reg = -1;

cstate->prevlinktype = cstate->outermostlinktype;
cstate->off_prevlinkhdr.constant_part = 0;
cstate->off_prevlinkhdr.is_variable = 0;
cstate->off_prevlinkhdr.reg = -1;
cstate->off_outermostlinkhdr = &(cstate->off_linkhdr);

cstate->linktype = cstate->outermostlinktype;
cstate->off_linkhdr.constant_part = 0;
Expand Down Expand Up @@ -1721,7 +1714,6 @@ init_linktype(compiler_state_t *cstate, pcap_t *p)
break;
}

cstate->off_outermostlinkhdr = cstate->off_prevlinkhdr = cstate->off_linkhdr;
return (0);
}

Expand Down Expand Up @@ -2370,7 +2362,7 @@ gen_load_prism_llprefixlen(compiler_state_t *cstate)
* but no known software generates headers that aren't 144
* bytes long.
*/
if (cstate->off_linkhdr.reg != -1) {
if (cstate->off_outermostlinkhdr->reg != -1) {
/*
* Load the cookie.
*/
Expand Down Expand Up @@ -2432,7 +2424,7 @@ gen_load_prism_llprefixlen(compiler_state_t *cstate)
* loading the length of the AVS header.
*/
s2 = new_stmt(cstate, BPF_ST);
s2->s.k = cstate->off_linkhdr.reg;
s2->s.k = cstate->off_outermostlinkhdr->reg;
sappend(s1, s2);
sjcommon->s.jf = s2;

Expand All @@ -2459,7 +2451,7 @@ gen_load_avs_llprefixlen(compiler_state_t *cstate)
* generated uses that prefix, so we don't need to generate any
* code to load it.)
*/
if (cstate->off_linkhdr.reg != -1) {
if (cstate->off_outermostlinkhdr->reg != -1) {
/*
* The 4 bytes at an offset of 4 from the beginning of
* the AVS header are the length of the AVS header.
Expand All @@ -2473,7 +2465,7 @@ gen_load_avs_llprefixlen(compiler_state_t *cstate)
* it.
*/
s2 = new_stmt(cstate, BPF_ST);
s2->s.k = cstate->off_linkhdr.reg;
s2->s.k = cstate->off_outermostlinkhdr->reg;
sappend(s1, s2);

/*
Expand All @@ -2499,7 +2491,7 @@ gen_load_radiotap_llprefixlen(compiler_state_t *cstate)
* generated uses that prefix, so we don't need to generate any
* code to load it.)
*/
if (cstate->off_linkhdr.reg != -1) {
if (cstate->off_outermostlinkhdr->reg != -1) {
/*
* The 2 bytes at offsets of 2 and 3 from the beginning
* of the radiotap header are the length of the radiotap
Expand Down Expand Up @@ -2534,7 +2526,7 @@ gen_load_radiotap_llprefixlen(compiler_state_t *cstate)
* it.
*/
s2 = new_stmt(cstate, BPF_ST);
s2->s.k = cstate->off_linkhdr.reg;
s2->s.k = cstate->off_outermostlinkhdr->reg;
sappend(s1, s2);

/*
Expand Down Expand Up @@ -2567,7 +2559,7 @@ gen_load_ppi_llprefixlen(compiler_state_t *cstate)
* into the register assigned to hold that length, if one has
* been assigned.
*/
if (cstate->off_linkhdr.reg != -1) {
if (cstate->off_outermostlinkhdr->reg != -1) {
/*
* The 2 bytes at offsets of 2 and 3 from the beginning
* of the radiotap header are the length of the radiotap
Expand Down Expand Up @@ -2602,7 +2594,7 @@ gen_load_ppi_llprefixlen(compiler_state_t *cstate)
* it.
*/
s2 = new_stmt(cstate, BPF_ST);
s2->s.k = cstate->off_linkhdr.reg;
s2->s.k = cstate->off_outermostlinkhdr->reg;
sappend(s1, s2);

/*
Expand Down Expand Up @@ -2659,7 +2651,7 @@ gen_load_802_11_header_len(compiler_state_t *cstate, struct slist *s, struct sli
* header.
*
* Otherwise, the length of the prefix preceding the link-layer
* header is "off_outermostlinkhdr.constant_part".
* header is "off_outermostlinkhdr->constant_part".
*/
if (s == NULL) {
/*
Expand All @@ -2669,10 +2661,10 @@ gen_load_802_11_header_len(compiler_state_t *cstate, struct slist *s, struct sli
* Load the length of the fixed-length prefix preceding
* the link-layer header (if any) into the X register,
* and store it in the cstate->off_linkpl.reg register.
* That length is off_outermostlinkhdr.constant_part.
* That length is off_outermostlinkhdr->constant_part.
*/
s = new_stmt(cstate, BPF_LDX|BPF_IMM);
s->s.k = cstate->off_outermostlinkhdr.constant_part;
s->s.k = cstate->off_outermostlinkhdr->constant_part;
}

/*
Expand Down Expand Up @@ -2758,7 +2750,7 @@ gen_load_802_11_header_len(compiler_state_t *cstate, struct slist *s, struct sli
* annoying padding don't have multiple antennae and therefore
* do not generate radiotap headers with multiple presence words.
*/
if (cstate->linktype == DLT_IEEE802_11_RADIO) {
if (cstate->outermostlinktype == DLT_IEEE802_11_RADIO) {
/*
* Is the IEEE80211_RADIOTAP_FLAGS bit (0x0000002) set
* in the first presence flag word?
Expand Down Expand Up @@ -2872,9 +2864,9 @@ insert_compute_vloffsets(compiler_state_t *cstate, struct block *b)
* includes the variable part of the header. Therefore,
* if nobody else has allocated a register for the link
* header and we need it, do it now. */
if (cstate->off_linkpl.reg != -1 && cstate->off_linkhdr.is_variable &&
cstate->off_linkhdr.reg == -1)
cstate->off_linkhdr.reg = alloc_reg(cstate);
if (cstate->off_linkpl.reg != -1 && cstate->off_outermostlinkhdr->is_variable &&
cstate->off_outermostlinkhdr->reg == -1)
cstate->off_outermostlinkhdr->reg = alloc_reg(cstate);

/*
* For link-layer types that have a variable-length header
Expand Down Expand Up @@ -8956,8 +8948,7 @@ gen_vlan(compiler_state_t *cstate, bpf_u_int32 vlan_num, int has_vlan_tag)
/* Verify that this is the outer part of the packet and
* not encapsulated somehow. */
if (cstate->vlan_stack_depth == 0 && !cstate->off_linkhdr.is_variable &&
cstate->off_linkhdr.constant_part ==
cstate->off_outermostlinkhdr.constant_part) {
cstate->off_outermostlinkhdr == &(cstate->off_linkhdr)) {
/*
* Do we need special VLAN handling?
*/
Expand Down