ef: add llc, stp, stp_rst and stp_tcn headers for 802.1D/802.1Q BPDUs

CMakeLists.txt

@@ -72,6 +72,7 @@ add_library(libef STATIC
     src/ef-igmp.c
     src/ef-ipv4.c
     src/ef-ipv6.c
+    src/ef-llc.c
     src/ef-mld.c
     src/ef-mrp.c
     src/ef-oam.c
@@ -82,6 +83,7 @@ add_library(libef STATIC
     src/ef-profinet.c
     src/ef-ptp.c
     src/ef-rate.c
+    src/ef-stp.c
     src/ef-sv.c
     src/ef-txring.c
     src/ef-udp.c
@@ -127,6 +129,8 @@ add_executable(ef-tests
     test/test-mld-zero-width.cxx
     test/test-rate-limit.cxx
     test/test-rx-ign.cxx
+    test/test-llc.cxx
+    test/test-stp.cxx
 )
 target_compile_options(ef-tests PRIVATE ${EF_SANITIZE_FLAGS})
 

fuzz/ef.dict

@@ -46,6 +46,14 @@
 "mrp_topo"
 "mrp_tst"
 
+# Headers LLC
+"llc"
+
+# Headers STP
+"stp"
+"stp_rst"
+"stp_tcn"
+
 # Headers PTP
 "ptp-announce"
 "ptp-follow-up"
@@ -168,6 +176,31 @@
 "hdr-flagField"
 "hdr-logMessageInterval"
 
+# Field names LLC
+"dsap"
+"ssap"
+"ctrl"
+
+# Field names STP
+"tc"
+"proposal"
+"role"
+"learning"
+"forwarding"
+"agreement"
+"tcack"
+"root_prio"
+"root_mac"
+"root_cost"
+"bridge_prio"
+"bridge_mac"
+"port"
+"msg_age"
+"max_age"
+"hello"
+"fwd_delay"
+"v1_len"
+
 # Field names OAM
 "opcode"
 "mel"

src/ef-llc.c

@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include "ef.h"
+
+// IEEE 802.2 Logical Link Control. An LLC header is preceded by a length and
+// not by an EtherType, so we compute the 802.3 length and write it into the
+// "et" field of the header below us -- eth, or the outermost VLAN tag, both
+// of which carry that field last.
+//
+// This works because frame_to_buf() runs frame_fill_defaults from the top of
+// the stack downwards: by the time eth_fill_defaults() calls
+// ether_type_fill_defaults(), et->val is already set and is left alone.
+static int llc_fill_defaults(struct frame *f, int stack_idx) {
+    char buf[16];
+    int i, len = 0;
+    hdr_t *ll;
+    field_t *et;
+
+    if (stack_idx < 1)
+        return 0;
+
+    ll = f->stack[stack_idx - 1];
+    et = find_field(ll, "et");
+
+    // An explicit "et" on the command line wins over the computed length.
+    if (!et || et->val)
+        return 0;
+
+    for (i = stack_idx; i < f->stack_size; ++i)
+        len += f->stack[i]->size;
+
+    // 802.3 clause 3.2.6: a type/length value above 1500 is not a length,
+    // and from 1536 up it is read as an EtherType. Refuse to emit one rather
+    // than silently write a frame the receiver will misparse.
+    if (len > 1500) {
+        pe("llc: 802.3 length %d exceeds 1500, set \"et\" explicitly\n",
+           len);
+        return -1;
+    }
+
+    snprintf(buf, 16, "%d", len);
+    buf[15] = 0;
+    et->val = parse_bytes(buf, 2);
+
+    return 0;
+}
+
+static field_t LLC_FIELDS[] = {
+    { .name = "dsap",
+      .help = "Destination Service Access Point, e.g. 0x42 for STP",
+      .bit_width =   8 },
+    { .name = "ssap",
+      .help = "Source Service Access Point, e.g. 0x42 for STP",
+      .bit_width =   8 },
+    { .name = "ctrl",
+      .help = "Control, one byte for U-format frames, e.g. 0x03 for UI",
+      .bit_width =   8 },
+};
+
+static hdr_t HDR_LLC = {
+    .name = "llc",
+    .help = "IEEE 802.2 LLC, sets the 802.3 length below it, e.g. llc stp",
+    .fields = LLC_FIELDS,
+    .fields_size = sizeof(LLC_FIELDS) / sizeof(LLC_FIELDS[0]),
+    .frame_fill_defaults = llc_fill_defaults,
+    .parser = hdr_parse_fields,
+};
+
+void llc_init() {
+    def_offset(&HDR_LLC);
+    def_val(&HDR_LLC, "dsap", "0x42");
+    def_val(&HDR_LLC, "ssap", "0x42");
+    def_val(&HDR_LLC, "ctrl", "0x03");
+
+    hdr_tmpls[HDR_TMPL_LLC] = &HDR_LLC;
+}
+
+void llc_uninit() {
+    uninit_frame_data(&HDR_LLC);
+
+    hdr_tmpls[HDR_TMPL_LLC] = 0;
+}