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Commit 650657cc authored by Adam Wujek's avatar Adam Wujek 💬
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lib/snmp: recalculate sizes of fields when returning error 

When snmpset is performed on not existing or read only OID, then response
packet does not contain to-be-set value. Due to that, returning packet is
shorter. It is necessary to recalculate sizes of the fields inside the response
packet.
Signed-off-by: Adam Wujek's avatarAdam Wujek <adam.wujek@cern.ch>
parent 5a833368
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Showing with 32 additions and 17 deletions
lib/snmp.c
View file @ 650657cc
......@@ -230,6 +230,7 @@ static int set_p(uint8_t *buf, struct snmp_oid *obj);
static int set_ptp_config(uint8_t *buf, struct snmp_oid *obj);
static void print_oid_verbose(uint8_t *oid, int len);
static void snmp_fix_size(uint8_t *buf, int size);
static uint8_t oid_wrpcVersionGroup[] = {0x2B,6,1,4,1,96,101,1,1};
static uint8_t oid_wrpcTimeGroup[] = {0x2B,6,1,4,1,96,101,1,2};
......@@ -1138,6 +1139,31 @@ static void print_oid_verbose(uint8_t *oid, int len)
snmp_verbose(".%d", *(oid + i));
}
/* fix sizes of fields in the SNMP packet */
static void snmp_fix_size(uint8_t *buf, int size)
{
int remain;
int a_i, h_i;
size--;
/* now fix all size fields and change PDU */
for (a_i = 0, h_i = 0; a_i < sizeof(match_array); a_i++, h_i++) {
remain = size - h_i;
if (match_array[a_i] == BYTE_PDU)
buf[h_i] = SNMP_GET_RESPONSE;
if (match_array[a_i] == BYTE_REQ_SIZE) {
h_i += buf[h_i];
continue;
}
if (match_array[a_i] != BYTE_SIZE)
continue;
snmp_verbose("%s: offset %i 0x%02x is len %i\n", __func__,
h_i, h_i, remain);
buf[h_i] = remain;
}
}
/* prepare packet to return error, leave the rest of packet as it was */
static uint8_t snmp_prepare_error(uint8_t *buf, uint8_t error)
{
......@@ -1160,7 +1186,10 @@ static uint8_t snmp_prepare_error(uint8_t *buf, uint8_t error)
shift += min(oid_len, MAX_OID_LEN);
/* write ASN_NULL after the OID */
buf[BYTE_OIDLEN_INDEX_i + shift + 1] = ASN_NULL;
ret_size = buf[BYTE_PACKET_SIZE_i] + 2;
buf[BYTE_OIDLEN_INDEX_i + shift + 2] = 0;
ret_size = BYTE_OIDLEN_INDEX_i + shift + 2 + 1;
/* recalculate sizes of the fields inside packet */
snmp_fix_size(buf, ret_size);
snmp_verbose("%s: error returning %i bytes\n", __func__, ret_size);
return ret_size;
}
......@@ -1319,26 +1348,12 @@ static int snmp_respond(uint8_t *buf)
return snmp_prepare_error(buf, SNMP_ERR_NOSUCHNAME);
}
/* now fix all size fields and change PDU */
for (a_i = 0, h_i = 0; a_i < sizeof(match_array); a_i++, h_i++) {
int remain = newbuf - buf - h_i - 1;
if (match_array[a_i] == BYTE_PDU)
buf[h_i] = SNMP_GET_RESPONSE;
if (match_array[a_i] == BYTE_REQ_SIZE) {
h_i += buf[h_i];
continue;
}
if (match_array[a_i] != BYTE_SIZE)
continue;
snmp_verbose("%s: offset %i 0x%02x is len %i\n", h_i, h_i,
__func__, remain);
buf[h_i] = remain;
}
snmp_fix_size(buf, newbuf - buf);
snmp_verbose("%s: returning %i bytes\n", __func__, newbuf - buf);
return newbuf - buf;
}
/* receive snmp through the UDP mechanism */
static int snmp_poll(void)
{
......
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