[Net-snmp-patches] [ net-snmp-Feature Requests-1439599 ] Providing specific MAC address for engineIDType 3

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Feature Requests item #1439599, was opened at 2006-02-27 14:50
Message generated for change (Tracker Item Submitted) made by Item Submitter
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: OferMotorola (grr1967)
Assigned to: Nobody/Anonymous (nobody)
Summary: Providing specific MAC address for engineIDType 3

Initial Comment:

The snmpd.conf token engineIDType 3 along with 
engineIDNic <eth interface> allows the engineID to be 
taken from the MAC address of a given ethernet 
interface.

There are cases that you want to provide a specific  
MAC address instead of dynamically loading it from an 
ethernet interface. 

One solution to this issue can be to allow the 
combination of engineIDType 3 with engineID, so in 
snmpd.conf it will be written as:

engineIDType 3 
engineID     001122334455   

The modifications to the code in this case would be:

1) Adding an "internal" ENGINEID_TYPE to snmpv3.h
#define ENGINEID_TYPE_MACADDR_HEX 127

2) In snmpv3.c change:
    if (NULL != text) {
        if (engineIDType == ENGINEID_TYPE_MACADDR)
            engineIDType = localEngineIDType = 
ENGINEID_TYPE_MACADDR_HEX;
        else
            engineIDType = localEngineIDType = 
ENGINEID_TYPE_TEXT;
    }
to allow a combination of MACADDR + text:
    if (NULL != text) {
        if (engineIDType == ENGINEID_TYPE_MACADDR)
            engineIDType = localEngineIDType = 
ENGINEID_TYPE_MACADDR_HEX;
        else
            engineIDType = localEngineIDType = 
ENGINEID_TYPE_TEXT;
    }

3) take into account the length (snmpv3.c)
    case ENGINEID_TYPE_MACADDR_HEX:       /* MAC 
address given as hex */
        len += 6;               /* + 6 bytes for MAC 
address */
        break;

4) And finally do the conversion from hex to binary 
and append to the engineID buffer (also in snmpv3.c)
    case ENGINEID_TYPE_MACADDR_HEX:
        {
            int             x;
            bufp[4] = ENGINEID_TYPE_MACADDR;
            memset(&bufp[5], 0, 6);
 
            /*
             * use default NIC if none provided
             */
 
            if (NULL != text) {
                size_t out_len = 0;
                size_t buf_len = 6;
                u_char *mac_addr = (u_char *)malloc
(buf_len);
                x = netsnmp_hex_to_binary(&mac_addr, 
&buf_len, &out_len,
                                          0, /*do not 
allow realloc*/
                                          text, 
NULL /*no delim*/);
                if (x == 0)
                    snmp_log(LOG_ERR, "Invalid MAC 
address specified '%s'\n",
                                      text);
                else if (buf_len != out_len)
                    snmp_log(LOG_ERR, "MAC address '%
s' is of wrong length\n",
                                      text);
                else
                    memcpy(&bufp[5], mac_addr, 
buf_len);
                free(mac_addr);

Another possible solution would be to add a new token, 
like engineIDMac to provide the MAC and thus not using 
the engineID which might raise backword compatibility 
issues.

            }
            
else                                              
            
{                                                 
                snmp_log
(LOG_ERR,                             
                   "Missing engineID token to specify 
MAC address\n");      
            }                                          
       
        }                                              
       
        break;    

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