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encode options that are longer than 255 octets. Helps with #2601
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this currently only works for RFC attributes.  A fix for TLVs
is the next step
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@alandekok
alandekok committed Apr 5, 2019
1 parent 3d07585 commit 71d021f
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Showing 2 changed files with 120 additions and 12 deletions.
121 changes: 109 additions & 12 deletions src/protocols/dhcpv4/encode.c
View file
Expand Up @@ -138,6 +138,84 @@ static ssize_t encode_value(uint8_t *out, size_t outlen,
return p - out;
}


/** Extend an encoded option in-place.
*
* @param[in] start buffer where the option starts
* @param[in] end where we must stop writing
* @param[in] p buffer where the current data resides
* @param[in] len length of the data being written
* @return
* - NULL if we can't extend the option
* - !NULL which is the start of the next option
*/
static uint8_t *extend_option(uint8_t *start, uint8_t *end, uint8_t *p, int len)
{
int headers;
uint8_t *out = start;

/*
* How many extra headers we will need to add.
*/
headers = ((out[1] + len) / 255) * 2;

/*
* No room for the new headers and data, we're done.
*/
if ((out + out[1] + headers + len) > end) {
return NULL;
}

/*
* Moving the same data repeatedly in a loop is simpler
* and less error-prone than anything smarter.
*/
while (len > 0) {
int sublen;

/*
* Figure out how much data goes into this
* option, and how much data we have to move out
* of the way.
*/
sublen = 255 - out[1];
if (sublen > len) sublen = len;

/*
* Add in the data left at the current pointer.
*/
out[1] += sublen;
len -= sublen;

/*
* Nothing more to do? Exit.
*/
if (!len) {
break;
}

/*
* The current option is full. So move the
* trailing data up by 2 bytes. Then add a new
* header, and keep looping in order to process
* the next chunk.
*/
p += sublen;
memmove(p + 2, p, len);

/*
* Build the new header, then jump to it and use it.
*/
p[0] = out[0];
p[1] = 0;
out = p;
p += 2;
}

return out;
}


/** Write out an RFC option header and option data
*
* @note May coalesce options with fixed width values
Expand All @@ -159,6 +237,7 @@ static ssize_t encode_rfc_hdr(uint8_t *out, ssize_t outlen,
{
ssize_t len;
uint8_t *p = out;
uint8_t *start, *end;
fr_dict_attr_t const *da = tlv_stack[depth];
VALUE_PAIR *vp = fr_cursor_current(cursor);

Expand All @@ -172,13 +251,9 @@ static ssize_t encode_rfc_hdr(uint8_t *out, ssize_t outlen,
out[0] = da->attr & 0xff;
out[1] = 0; /* Length of the value only (unlike RADIUS) */

outlen -= 2;
p += 2;

/*
* Check here so we get the full 255 bytes
*/
if (outlen > UINT8_MAX) outlen = UINT8_MAX;
start = out;
end = out + outlen;

/*
* DHCP options with the same number (and array flag set)
Expand All @@ -190,7 +265,21 @@ static ssize_t encode_rfc_hdr(uint8_t *out, ssize_t outlen,
do {
VALUE_PAIR *next;

len = encode_value(p, outlen - out[1], tlv_stack, depth, cursor, encoder_ctx);
/*
* As a quick hack, check if there's enough room
* for fixed-size attributes. If we're encoding
* the second or later value into this option,
* AND we're encoding fixed size values, AND
* there's no room for the next fixed-size value,
* then don't encode this VP.
*/
if (out[1] && vp->da->flags.array &&
(dict_attr_sizes[vp->da->type][0] == dict_attr_sizes[vp->da->type][1]) &&
(out[1] + dict_attr_sizes[vp->da->type][0]) > 255) {
break;
}

len = encode_value(p, end - p, tlv_stack, depth, cursor, encoder_ctx);
if (len < -1) return len;
if (len == -1) {
FR_PROTO_TRACE("No more space in option");
Expand All @@ -203,19 +292,27 @@ static ssize_t encode_rfc_hdr(uint8_t *out, ssize_t outlen,

FR_PROTO_STACK_PRINT(tlv_stack, depth);
FR_PROTO_TRACE("Encoded value is %zu byte(s)", len);
FR_PROTO_HEX_DUMP(out, (p - out), NULL);
FR_PROTO_HEX_DUMP(start, (p - start), NULL);

p += len;
out[1] += len;
if ((out[1] + len) <= 255) {
p += len;
out[1] += len;
FR_PROTO_TRACE("%u byte(s) available in option", 255 - out[1]);

} else {
out = extend_option(out, end, p, len);
if (!out) break;

FR_PROTO_TRACE("%zu byte(s) available in option", outlen - out[1]);
p = out + 2;
p += out[1];
}

next = fr_cursor_current(cursor);
if (!next || (vp->da != next->da)) break;
vp = next;
} while (vp->da->flags.array);

return p - out;
return p - start;
}

/** Write out a TLV header (and any sub TLVs or values)
Expand Down
11 changes: 11 additions & 0 deletions src/tests/unit/dhcpv4.txt
View file
Expand Up @@ -46,3 +46,14 @@ data 52 e3 01 e1 6f 68 20 68 61 69 20 74 68 69 73 20 69 73 20 61 6e 20 61 67 65
# An empty option (Rapid Commit)
encode-pair DHCP-Rapid-Commit = ''
data 50 00

# 255 bytes are OK
encode-pair DHCP-Domain-Name = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
data 0f ff 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78

encode-pair DHCP-Merit-Dump-File="1234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456"
data 0e ff 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 0e 01 36

# A very long option should be split automatically
encode-pair DHCP-Domain-Name = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
data 0f ff 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 0f 2d 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78 78

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