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#184 - Experimental code for unpacking MPLS labels, finding the bottom-of-stack and extracting IPv4 or IPv6 payload. Does not supported VLANs nested inside VPLS. Needs considerably more testing.

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This commit is contained in:
Herbert Wolverson
2023-01-12 18:48:53 +00:00
parent f79f850079
commit d9ae80e56f
2 changed files with 72 additions and 0 deletions
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43
src/rust/lqos_sys/src/bpf/common/dissector.h
View File

@@ -62,6 +62,20 @@ struct pppoe_proto
#define PPP_IP 0x21
#define PPP_IPV6 0x57
// Representation of an MPLS label
struct mpls_label {
__be32 entry;
};
#define MPLS_LS_LABEL_MASK 0xFFFFF000
#define MPLS_LS_LABEL_SHIFT 12
#define MPLS_LS_TC_MASK 0x00000E00
#define MPLS_LS_TC_SHIFT 9
#define MPLS_LS_S_MASK 0x00000100
#define MPLS_LS_S_SHIFT 8
#define MPLS_LS_TTL_MASK 0x000000FF
#define MPLS_LS_TTL_SHIFT 0
// Constructor for a dissector
// Connects XDP/TC SKB structure to a dissector structure.
// Arguments:
@@ -195,6 +209,35 @@ static __always_inline bool dissector_find_l3_offset(
offset += PPPOE_SES_HLEN;
}
break;
// WARNING/TODO: Here be dragons; this needs testing.
case ETH_P_MPLS_UC:
case ETH_P_MPLS_MC: {
if SKB_OVERFLOW_OFFSET(dissector->start, dissector-> end,
offset, mpls_label)
{
return false;
}
struct mpls_label * mpls = (struct mpls_label *)
(dissector->start + offset);
// Are we at the bottom of the stack?
offset += 4; // 32-bits
if (mpls->entry & MPLS_LS_S_MASK) {
// We've hit the bottom
if SKB_OVERFLOW_OFFSET(dissector->start, dissector->end,
offset, iphdr)
{
return false;
}
struct iphdr * iph = (struct iphdr *)(dissector->start + offset);
switch (iph->version) {
case 4: eth_type = ETH_P_IP; break;
case 6: eth_type = ETH_P_IPV6; break;
default: return false;
}
}
} break;
// We found something we don't know how to handle - bail out
default:
return false;

29
src/rust/lqos_sys/src/bpf/common/dissector_tc.h
View File

@@ -141,6 +141,35 @@ static __always_inline bool tc_dissector_find_l3_offset(
offset += PPPOE_SES_HLEN;
}
break;
// WARNING/TODO: Here be dragons; this needs testing.
case ETH_P_MPLS_UC:
case ETH_P_MPLS_MC: {
if SKB_OVERFLOW_OFFSET(dissector->start, dissector-> end,
offset, mpls_label)
{
return false;
}
struct mpls_label * mpls = (struct mpls_label *)
(dissector->start + offset);
// Are we at the bottom of the stack?
offset += 4; // 32-bits
if (mpls->entry & MPLS_LS_S_MASK) {
// We've hit the bottom
if SKB_OVERFLOW_OFFSET(dissector->start, dissector->end,
offset, iphdr)
{
return false;
}
struct iphdr * iph = (struct iphdr *)(dissector->start + offset);
switch (iph->version) {
case 4: eth_type = ETH_P_IP; break;
case 6: eth_type = ETH_P_IPV6; break;
default: return false;
}
}
} break;
// We found something we don't know how to handle - bail out
default:
return false;