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Flowspec: Fix IPv6 prefix when offset is not multiple of 8

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Current implementation handles flowspec prefix length and offset only
in bytes, but RFC 8956 (Dissemination of Flow Specification Rules for
IPv6) Section 3.1 [1] and example in Section 3.8.2 [2] states the
pattern should begin right after offset *bits*.

For example, pattern "::1:1234:5678:9800:0/60-104" is currently
serialized as "02 68 3c 01 12 34 56 78 98", but it should shift its
pattern 4 more bits to the left: "02 68 3c 11 23 45 67 89 80".

This patch implements shifting left/right for IPv6 type and use it to
correct the behaviour. Test data are replaced with the correct ones.

Minor changes and test vectors done by committer.

[1]: https://www.rfc-editor.org/rfc/rfc8956.html#section-3.1
[2]: https://www.rfc-editor.org/rfc/rfc8956.html#section-3.8.2
This commit is contained in:
Eric Long 2024-10-16 21:32:36 +02:00 committed by Ondrej Zajicek
parent 6f9ccfae9e
commit 072821e55e
5 changed files with 120 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
lib/flowspec.c
View File

@ -293,13 +293,9 @@ flow_read_ip4_part(const byte *part)
static inline ip6_addr
flow_read_ip6(const byte *px, uint pxlen, uint pxoffset)
{
uint floor_offset = BYTES(pxoffset - (pxoffset % 8));
uint ceil_len = BYTES(pxlen);
ip6_addr ip = IP6_NONE;
memcpy(((byte *) &ip) + floor_offset, px, ceil_len - floor_offset);
return ip6_ntoh(ip);
memcpy(&ip, px, BYTES(pxlen - pxoffset));
return ip6_shift_right(ip6_ntoh(ip), pxoffset);
}
ip6_addr
@ -476,7 +472,7 @@ flow_validate(const byte *nlri, uint len, int ipv6)
uint pxoffset = *pos++;
if (pxoffset > IP6_MAX_PREFIX_LENGTH || pxoffset > pxlen)
return FLOW_ST_EXCEED_MAX_PREFIX_OFFSET;
bytes -= pxoffset / 8;
bytes = BYTES(pxlen - pxoffset);
}
pos += bytes;
@ -749,12 +745,12 @@ flow_builder6_add_pfx(struct flow_builder *fb, const net_addr_ip6 *n6, u32 pxoff
if (!builder_add_prepare(fb))
return 0;
ip6_addr ip6 = ip6_hton(n6->prefix);
ip6_addr ip6 = ip6_hton(ip6_shift_left(n6->prefix, pxoffset));
BUFFER_PUSH(fb->data) = fb->this_type;
BUFFER_PUSH(fb->data) = n6->pxlen;
BUFFER_PUSH(fb->data) = pxoffset;
push_pfx_to_buffer(fb, BYTES(n6->pxlen) - (pxoffset / 8), ((byte *) &ip6) + (pxoffset / 8));
push_pfx_to_buffer(fb, BYTES(n6->pxlen - pxoffset), ((byte *) &ip6));
builder_add_finish(fb);
return 1;

4
lib/flowspec_test.c
View File

@ -542,7 +542,7 @@ t_builder6(void)
const net_addr_flow6 *expect = NET_ADDR_FLOW6_NLRI(
0,
FLOW_TYPE_DST_PREFIX, 103, 61, 0x01, 0x12, 0x34, 0x56, 0x78, 0x98,
FLOW_TYPE_DST_PREFIX, 103, 61, 0x22, 0x46, 0x8a, 0xcf, 0x13, 0x00,
FLOW_TYPE_SRC_PREFIX, 8, 0, 0xc0,
FLOW_TYPE_NEXT_HEADER, 0x80, 0x06,
FLOW_TYPE_PORT, 0x03, 0x89, 0x45, 0x8b, 0x91, 0x1f, 0x90,
@ -678,7 +678,7 @@ t_formatting6(void)
expect[0] = "flow6 { dst ::1:1234:5678:9800:0/103 offset 61; src c000::/8; next header 6; port 20..40,273; label < 500000; }";
input[0] = NET_ADDR_FLOW6_NLRI(
0,
FLOW_TYPE_DST_PREFIX, 103, 61, 0x01, 0x12, 0x34, 0x56, 0x78, 0x98,
FLOW_TYPE_DST_PREFIX, 103, 61, 0x22, 0x46, 0x8a, 0xcf, 0x13, 0x00,
FLOW_TYPE_SRC_PREFIX, 8, 0, 0xc0,
FLOW_TYPE_NEXT_HEADER, 0x81, 0x06,
FLOW_TYPE_PORT, 0x03, 20, 0x45, 40, 0x91, 0x01, 0x11,

48
lib/ip.c
View File

@ -156,6 +156,54 @@ ip6_classify(ip6_addr *a)
}
/*
* IPv6 bit shifting
*/
ip6_addr
ip6_shift_left(ip6_addr a, uint bits)
{
if (bits == 0)
return a;
if (bits > 127)
return IP6_NONE;
int words = bits / 32;
int rem = bits % 32;
for (int i = 0; i < 3 - words; i++)
a.addr[i] = (a.addr[i + words] << rem) |
(rem ? (a.addr[i + words + 1] >> (32 - rem)) : 0);
a.addr[3 - words] = a.addr[3] << rem;
memset(&a.addr[4 - words], 0, words * 4);
return a;
}
ip6_addr
ip6_shift_right(ip6_addr a, uint bits)
{
if (bits == 0)
return a;
if (bits > 127)
return IP6_NONE;
int words = bits / 32;
int rem = bits % 32;
for (int i = 3; i > words; i--)
a.addr[i] = (a.addr[i - words] >> rem) |
(rem ? (a.addr[i - words - 1] << (32 - rem)) : 0);
a.addr[words] = a.addr[0] >> rem;
memset(&a.addr[0], 0, words * 4);
return a;
}
/*
* Conversion of IPv6 address to presentation format and vice versa.

3
lib/ip.h
View File

@ -354,6 +354,9 @@ static inline ip4_addr ip4_setbits(ip4_addr a, uint pos, uint val)
static inline ip6_addr ip6_setbits(ip6_addr a, uint pos, uint val)
{ a.addr[pos / 32] |= val << (31 - pos % 32); return a; }
ip6_addr ip6_shift_left(ip6_addr a, uint bits);
ip6_addr ip6_shift_right(ip6_addr a, uint bits);
static inline ip4_addr ip4_opposite_m1(ip4_addr a)
{ return _MI4(_I(a) ^ 1); }

62
lib/ip_test.c
View File

@ -231,6 +231,66 @@ t_ip6_prefix_equal(void)
return 1;
}
static int
t_ip6_shift_left(void)
{
ip6_addr a = ip6_build(0x8D0D8BDC, 0x1F04DB92, 0xE5117673, 0x70E54449);
struct { int n; ip6_addr val; } test_vectors[] = {
0, ip6_build(0x8D0D8BDC, 0x1F04DB92, 0xE5117673, 0x70E54449),
9, ip6_build(0x1B17B83E, 0x09B725CA, 0x22ECE6E1, 0xCA889200),
18, ip6_build(0x2F707C13, 0x6E4B9445, 0xD9CDC395, 0x11240000),
27, ip6_build(0xE0F826DC, 0x97288BB3, 0x9B872A22, 0x48000000),
36, ip6_build(0xF04DB92E, 0x51176737, 0x0E544490, 0x00000000),
45, ip6_build(0x9B725CA2, 0x2ECE6E1C, 0xA8892000, 0x00000000),
54, ip6_build(0xE4B9445D, 0x9CDC3951, 0x12400000, 0x00000000),
63, ip6_build(0x7288BB39, 0xB872A224, 0x80000000, 0x00000000),
72, ip6_build(0x11767370, 0xE5444900, 0x00000000, 0x00000000),
81, ip6_build(0xECE6E1CA, 0x88920000, 0x00000000, 0x00000000),
90, ip6_build(0xCDC39511, 0x24000000, 0x00000000, 0x00000000),
99, ip6_build(0x872A2248, 0x00000000, 0x00000000, 0x00000000),
108, ip6_build(0x54449000, 0x00000000, 0x00000000, 0x00000000),
117, ip6_build(0x89200000, 0x00000000, 0x00000000, 0x00000000),
126, ip6_build(0x40000000, 0x00000000, 0x00000000, 0x00000000),
128, ip6_build(0x00000000, 0x00000000, 0x00000000, 0x00000000),
};
for (uint i = 0; i < ARRAY_SIZE(test_vectors); i++)
bt_assert(ip6_equal(ip6_shift_left(a, test_vectors[i].n), test_vectors[i].val));
return 1;
}
static int
t_ip6_shift_right(void)
{
ip6_addr a = ip6_build(0x8D0D8BDC, 0x1F04DB92, 0xE5117673, 0x70E54449);
struct { int n; ip6_addr val; } test_vectors[] = {
0, ip6_build(0x8D0D8BDC, 0x1F04DB92, 0xE5117673, 0x70E54449),
9, ip6_build(0x004686C5, 0xEE0F826D, 0xC97288BB, 0x39B872A2),
18, ip6_build(0x00002343, 0x62F707C1, 0x36E4B944, 0x5D9CDC39),
27, ip6_build(0x00000011, 0xA1B17B83, 0xE09B725C, 0xA22ECE6E),
36, ip6_build(0x00000000, 0x08D0D8BD, 0xC1F04DB9, 0x2E511767),
45, ip6_build(0x00000000, 0x0004686C, 0x5EE0F826, 0xDC97288B),
54, ip6_build(0x00000000, 0x00000234, 0x362F707C, 0x136E4B94),
63, ip6_build(0x00000000, 0x00000001, 0x1A1B17B8, 0x3E09B725),
72, ip6_build(0x00000000, 0x00000000, 0x008D0D8B, 0xDC1F04DB),
81, ip6_build(0x00000000, 0x00000000, 0x00004686, 0xC5EE0F82),
90, ip6_build(0x00000000, 0x00000000, 0x00000023, 0x4362F707),
99, ip6_build(0x00000000, 0x00000000, 0x00000000, 0x11A1B17B),
108, ip6_build(0x00000000, 0x00000000, 0x00000000, 0x0008D0D8),
117, ip6_build(0x00000000, 0x00000000, 0x00000000, 0x00000468),
126, ip6_build(0x00000000, 0x00000000, 0x00000000, 0x00000002),
128, ip6_build(0x00000000, 0x00000000, 0x00000000, 0x00000000),
};
for (uint i = 0; i < ARRAY_SIZE(test_vectors); i++)
bt_assert(ip6_equal(ip6_shift_right(a, test_vectors[i].n), test_vectors[i].val));
return 1;
}
int
main(int argc, char *argv[])
{
@ -242,6 +302,8 @@ main(int argc, char *argv[])
bt_test_suite(t_ip6_ntop, "Converting ip6_addr struct to IPv6 string");
bt_test_suite(t_ip4_prefix_equal, "Testing ip4_prefix_equal()");
bt_test_suite(t_ip6_prefix_equal, "Testing ip6_prefix_equal()");
bt_test_suite(t_ip6_shift_left, "Testing ip6_shift_left()");
bt_test_suite(t_ip6_shift_right, "Testing ip6_shift_right()");
return bt_exit_value();
}