Simplification examples

The following are real before/after pairs, adapted from a RADIUS authentication module mid-migration to the new API. See API mapping for the function-by-function table these draw from.

One error check instead of one per call

Building an Access-Request used to mean checking every rc_avpair_add() call individually:

Legacy API

send = NULL;
if (rc_avpair_add(rh, &send, PW_USER_NAME, username, -1, 0) == NULL)
    goto fail;
if (rc_avpair_add(rh, &send, PW_USER_PASSWORD, password, -1, 0) == NULL)
    goto fail;
if (rc_avpair_add(rh, &send, PW_NAS_IDENTIFIER, nas_id, -1, 0) == NULL)
    goto fail;
/* ... repeated for every attribute ... */

With the new API, every add is unconditional and a single check at the end covers the whole batch:

New API

radcli_avp_list *send = radcli_avp_list_new();
radcli_avp_add_str_by_num(send, ctx, PW_USER_NAME, 0, username);
radcli_avp_add_bytes_by_num(send, ctx, PW_USER_PASSWORD, 0, password, password_len);
radcli_avp_add_str_by_num(send, ctx, PW_NAS_IDENTIFIER, 0, nas_id);
/* ... */
if (radcli_avp_list_error(send)) {
    radcli_avp_list_free(send);
    goto fail;
}

Appending a realm to User-Name only when the caller didn't already supply one

The legacy pattern hand-rolls the "does it already have a realm" check and the concatenation:

Legacy API

char namebuf[256];
if (strchr(username, '@') == NULL && default_realm[0] != '\0')
    snprintf(namebuf, sizeof(namebuf), "%s@%s", username, default_realm);
else
    snprintf(namebuf, sizeof(namebuf), "%s", username);
rc_avpair_add(rh, &send, PW_USER_NAME, namebuf, -1, 0);

radcli_avp_add_username() does the check and, passed NULL for realm, reaches for ctx's own default_realm config option, so an application whose realm policy is just "whatever the config file says" never reads that option out itself:

New API

radcli_avp_add_username(send, ctx, username, NULL);

Reading a 64-bit accounting counter

RFC 2869's Acct-Input/Output-Gigawords exists because RADIUS has no 64-bit counter attribute: a 64-bit octet count is really two 32-bit attributes, and the legacy API leaves combining them to the caller:

Legacy API

VALUE_PAIR *octets = rc_avpair_get(received, PW_ACCT_INPUT_OCTETS, 0);
VALUE_PAIR *giga = rc_avpair_get(received, PW_ACCT_INPUT_GIGAWORDS, 0);
uint64_t total = octets ? octets->lvalue : 0;
if (giga)
    total += (uint64_t)giga->lvalue << 32;

radcli_avp_add_gigawords64()/radcli_avp_get_gigawords64() do the splitting/reassembly, including looking up octets' Gigawords counterpart from the dictionary rather than trusting the caller to get the pairing right:

New API

uint64_t total;
radcli_avp_get_gigawords64(ctx, received, d_acct_input_octets, &total);

Reading an RFC 8044 64-bit or ifid attribute

The legacy rc_attr_type enum predates RFC 8044 and has no integer64 or ifid type – attributes of those types come back as raw bytes that the caller must byte-swap by hand:

Legacy API

VALUE_PAIR *vp = rc_avpair_get(received, PW_SOME_INTEGER64_ATTR, 0);
uint64_t val = 0;
if (vp && vp->lvalue == 8) {
    unsigned char *p = (unsigned char *)vp->strvalue;
    for (int i = 0; i < 8; i++)
        val = (val << 8) | p[i];
}

The new dictionary understands RADCLI_TYPE_INTEGER64/RADCLI_TYPE_IFID natively, so radcli_avp_get_uint64_by_num() returns the decoded value in one call, byte order already handled:

New API

uint64_t val;
radcli_avp_get_uint64_by_num(received, ctx, PW_SOME_INTEGER64_ATTR, 0, &val);

Looking up and reading a well-known attribute in one call

The legacy pattern is a lookup call whose result feeds a second call:

Legacy API

VALUE_PAIR *vp = rc_avpair_get(received, PW_SESSION_TIMEOUT, 0);
uint32_t timeout = vp ? vp->lvalue : 0;

Which is manageable for one attribute, but the new API's _by_num() accessors fold "find the attribute" and "read it as this type" into a single typed call for every attribute type, including the ones (IPv6, IPv6/IPv4 prefixes, raw bytes, C strings) where the legacy struct's shared lvalue/strvalue fields otherwise need type-specific care:

New API

uint32_t timeout = 0;
radcli_avp_get_uint32_by_num(received, ctx, PW_SESSION_TIMEOUT, 0, &timeout);

For a reply attribute read repeatedly in a hot path, resolving its radcli_attr_def * once with radcli_dict_lookup_num() and reusing it across radcli_avp_get() calls (comparing by pointer identity, not attribute number) avoids repeating that lookup – see radcli2-avp-by-num.

Collecting a repeated attribute (Reply-Message) into one string

A server is free to send more than one Reply-Message in a single Access-Accept/-Reject/-Challenge (RFC 2865 SS5.16 – one attribute cannot hold more than 253 bytes, so a longer message is split across several occurrences), and applications that surface it to the end user – as a login-failure reason, or the prompt text of an interactive multi-factor challenge – need the whole message, not just the first fragment. That means every occurrence has to be walked and joined, not just the first one rc_avpair_get() would hand back:

Legacy API

char msg[256] = "";
VALUE_PAIR *vp = received;
while ((vp = rc_avpair_get(vp, PW_REPLY_MESSAGE, 0)) != NULL) {
    strlcat(msg, vp->strvalue, sizeof(msg));
    strlcat(msg, " ", sizeof(msg));
    vp = vp->next;
}

New API

char msg[256];
radcli_avp_concat_str_by_num(msg, sizeof(msg), received, ctx,
                              PW_REPLY_MESSAGE, 0, " ");