moving shared parts to snmp_utils

proto/snmp/snmp_utils.c

+/*
+ *	BIRD -- Simple Network Management Protocol (SNMP) helper functions
+ *
+ *      (c) 2022 Vojtech Vilimek <vojtech.vilimek@nic.cz>
+ *      (c) 2022 CZ.NIC z.s.p.o
+ *
+ *	Can be freely distributed and used under the terms of the GNU GPL.
+ *
+ */
+
+#include "snmp_utils.h"
+
+/**
+ * snmp_is_oid_empty - check if oid is null-valued 
+ * @oid: object identifier to check
+ *
+ * Test if the oid header is full of zeroes. For @oid NULL returns 0.
+ */
+int
+snmp_is_oid_empty(struct oid *oid)
+{
+  if (oid != NULL)
+    return oid->n_subid == 0 && oid->prefix == 0 && oid->include == 0;
+  else
+    return 0;
+}
+
+/**
+ * snmp_pkt_len - returns size of SNMP packet payload (without header)
+ * @buf: packet first byte
+ * @pkt: first byte past packet end
+ */
+size_t
+snmp_pkt_len(byte *buf, byte *pkt)
+{
+  return (pkt - buf) - AGENTX_HEADER_SIZE;
+}
+
+/**
+ * snmp_str_size - return in packet size of supplied string
+ * @str: measured string
+ *
+ * Returned value is string length aligned to 4 byte with 32bit length
+ * annotation included.
+ */
+size_t
+snmp_str_size(const char *str)
+{
+  return 4 + BIRD_ALIGN(strlen(str), 4);
+}
+
+/**
+ * snmp_oid_size - measure size of oid in bytes
+ * @o: object identifier to use
+ */
+uint
+snmp_oid_size(struct oid *o)
+{
+  //return 4 + o->n_subid * 4;
+  return 4 + (o->n_subid << 2);
+}
+
+/**
+ * snmp_vb_size - measure size of varbind in bytes
+ * @vb: variable binding to use
+ */
+uint
+snmp_varbind_size(struct agentx_varbind *vb)
+{
+  return snmp_oid_size(&vb->name) + 4;
+}
+
+struct agentx_varbind *
+snmp_create_varbind(byte *buf, struct oid *oid)
+{
+  struct agentx_varbind *vb = (void*) buf;
+  memcpy(&vb->name, oid, snmp_oid_size(oid));
+  return vb;
+}
+
+byte *snmp_fix_varbind(struct agentx_varbind *vb, struct oid *new)
+{
+  memcpy(&vb->name, new, snmp_oid_size(new));
+  return (void *) vb + snmp_varbind_size(vb);
+}
+
+/**
+ * snmp_oid_ip4_index - check IPv4 address validity in oid
+ * @o: object identifier holding ip address
+ * @start: index of first address id
+ */
+int
+snmp_valid_ip4_index(struct oid *o, uint start)
+{
+  if (start + 3 < o->n_subid)
+    return snmp_valid_ip4_index_unsafe(o, start);
+  else
+    return 0; // false
+}
+
+/**
+ * snmp_valid_ip4_index_unsafe - check validity of IPv4 address in oid
+ * @o: object identifier holding ip address
+ * @start: index of first address id
+ *
+ * This function is unsafe - no checks of object identifier ids
+ * length sufficiency is done.
+ */
+int
+snmp_valid_ip4_index_unsafe(struct oid *o, uint start)
+{
+  for (int i = 0; i < 4; i++)
+    if (o->ids[start + i] >= 256)
+      return 0;	// false
+ 
+  return 1; // true 
+}
+
+/**
+ * snmp_put_str - put string into SNMP PDU transcieve buffer
+ * @buf: pointer to first unoccupied buffer byte
+ * @str: string to place
+ *
+ * Handles all conditions specified by RFC, namely string length annotation
+ * and padding 4 byte alignment with zeroes. Return NULL if string is too large
+ * for SNMP message.
+ */
+byte *
+snmp_put_str(byte *buf, const char *str)
+{
+  uint len = strlen(str);
+  uint slen = BIRD_ALIGN(len, 4);
+
+  if (len > MAX_STR)
+    return NULL;
+
+  STORE_PTR(buf, len);
+
+  memcpy(buf + 4, str, len);
+
+  for (uint i = 0; i < slen - len; i++)
+    buf[len + i] = 0x00;  // PADDING
+
+  return buf + snmp_str_size(str);
+}
+
+byte *
+snmp_put_blank(byte *buf)
+{
+  STORE_PTR(buf, 0);
+  return buf + 4;
+}
+
+/**
+ * snmp_put_oid - put oid into SNMP PDU transcieve buffer
+ * @buf: pointer to first free buffer byte
+ * @oid: object identifier to use
+ */
+byte *
+snmp_put_oid(byte *buf, struct oid *oid)
+{
+  put_u8(buf, oid->n_subid);
+  put_u8(++buf, oid->prefix);
+  put_u8(++buf, oid->include);
+  put_u8(++buf, 0);  // PADDING
+
+  /* last increment */
+  ++buf;
+
+  /* copy OID data */
+#ifdef SNMP_NATIVE
+  for (uint i = 0; i < oid->n_subid; i++)
+    *(((u32 *) buf) + i) = oid->ids[i];
+#else
+  put_u32s(buf, oid->ids, oid->n_subid << 2);
+#endif
+
+  return buf + (oid->n_subid << 2);
+}
+
+/**
+ * snmp_put_fbyte - put one padded byte to SNMP PDU transcieve buffer
+ * @buf: pointer to free buffer byte
+ * @data: byte to use
+ *
+ * Put @data into buffer @buf with 3B zeroed padding.
+ */
+/* paste data at first byte in message
+ *   with 3B of padding
+ */
+byte *
+snmp_put_fbyte(byte *buf, u8 data)
+{
+  log(L_INFO "paste_fbyte()");
+  put_u8(buf, data);
+  put_u24(++buf, 0);  // PADDING
+  return buf + 3;
+}
+
+
+void
+snmp_oid_ip4_index(struct oid *o, uint start, ip4_addr addr)
+{
+  u32 temp = ip4_to_u32(addr);
+  STORE(o->ids[start], temp >> 24);
+  STORE(o->ids[start + 1], (temp >> 16) & 0xFF);
+  STORE(o->ids[start + 2], (temp >>  8) & 0xFF);
+  STORE(o->ids[start + 3], temp & 0xFF);
+}
+
+void snmp_oid_dump(struct oid *oid)
+{
+  log(L_WARN "OID DUMP ========");
+
+  if (oid == NULL)
+  {
+    log(L_WARN "is eqaul to NULL");
+    log(L_WARN "OID DUMP END ====");
+    log(L_WARN);
+    return;
+  }
+
+  else if (snmp_is_oid_empty(oid))
+  {
+    log(L_WARN "is empty");
+    log(L_WARN "OID DUMP END ====");
+    log(L_WARN);
+    return;
+  }
+
+  log(L_WARN "  #ids: %4u  prefix %3u  include: %5s",
+    oid->n_subid, oid->prefix, (oid->include)? "true" : "false");
+  log(L_WARN "IDS -------------");
+
+  for (int i = 0; i < oid->n_subid; i++)
+    log(L_WARN "  %2u:  %11u  ~ 0x%08X", i, oid->ids[i], oid->ids[i]);
+
+  log(L_WARN "OID DUMP END ====");
+  log(L_WARN);
+}

proto/snmp/snmp_utils.h

+#ifndef _BIRD_SNMP_UTILS_H_
+#define _BIRD_SNMP_UTILS_H_
+
+#include "subagent.h"
+
+size_t snmp_pkt_len(byte *buf, byte *pkt);
+size_t snmp_str_size(const char *str);
+int snmp_is_oid_empty(struct oid *oid);
+int snmp_valid_ip4_index(struct oid *o, uint start);
+int snmp_valid_ip4_index_unsafe(struct oid *o, uint start);
+uint snmp_oid_size(struct oid *o);
+uint snmp_varbind_size(struct agentx_varbind *vb);
+
+struct agentx_varbind *snmp_create_varbind(byte* buf, struct oid *oid);
+byte *snmp_fix_varbind(struct agentx_varbind *vb, struct oid *new);
+
+int snmp_oid_compare(struct oid *first, struct oid *second);
+
+byte *snmp_no_such_object(byte *buf, struct agentx_varbind *vb, struct oid *oid);
+byte *snmp_no_such_instance(byte *buf, struct agentx_varbind *vb, struct oid *oid);
+
+byte *snmp_put_str(byte *buf, const char *str);
+byte *snmp_put_blank(byte *buf);
+byte *snmp_put_oid(byte *buf, struct oid *oid);
+
+byte *snmp_put_fbyte(byte *buf, u8 data);
+
+void snmp_oid_ip4_index(struct oid *o, uint start, ip4_addr addr);
+
+void snmp_oid_dump(struct oid *oid);
+
+#endif