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Io.net: implement sortLookupResults
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Andrew Kelley
parent
676f1b492e
commit
4e887625d4
@ -132,9 +132,58 @@ pub const HostName = struct {
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}
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fn sortLookupResults(options: LookupOptions, result: LookupResult) !LookupResult {
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_ = options;
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_ = result;
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@panic("TODO");
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const addresses = options.addresses_buffer[0..result.addresses_len];
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// No further processing is needed if there are fewer than 2 results or
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// if there are only IPv4 results.
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if (addresses.len < 2) return result;
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const all_ip4 = for (addresses) |a| switch (a) {
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.ip4 => continue,
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.ip6 => break false,
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} else true;
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if (all_ip4) return result;
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// RFC 3484/6724 describes how destination address selection is
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// supposed to work. However, to implement it requires making a bunch
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// of networking syscalls, which is unnecessarily high latency,
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// especially if implemented serially. Furthermore, rules 3, 4, and 7
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// have excessive runtime and code size cost and dubious benefit.
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//
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// Therefore, this logic sorts only using values available without
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// doing any syscalls, relying on the calling code to have a
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// meta-strategy such as attempting connection to multiple results at
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// once and keeping the fastest response while canceling the others.
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const S = struct {
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pub fn lessThan(s: @This(), lhs: IpAddress, rhs: IpAddress) bool {
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return sortKey(s, lhs) < sortKey(s, rhs);
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}
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fn sortKey(s: @This(), a: IpAddress) i32 {
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_ = s;
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var da6: Ip6Address = .{
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.port = 65535,
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.bytes = undefined,
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};
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switch (a) {
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.ip6 => |ip6| {
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da6.bytes = ip6.bytes;
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da6.scope_id = ip6.scope_id;
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},
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.ip4 => |ip4| {
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da6.bytes[0..12].* = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff".*;
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da6.bytes[12..].* = ip4.bytes;
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},
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}
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const da6_scope: i32 = da6.scope();
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const da6_prec: i32 = da6.policy().prec;
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var key: i32 = 0;
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key |= da6_prec << 20;
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key |= (15 - da6_scope) << 16;
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return key;
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}
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};
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std.mem.sort(IpAddress, addresses, @as(S, .{}), S.lessThan);
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return result;
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}
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fn lookupDns(io: Io, options: LookupOptions) !LookupResult {
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@ -406,6 +455,14 @@ pub const Ip6Address = struct {
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Incomplete,
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};
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pub const Policy = struct {
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addr: [16]u8,
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len: u8,
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mask: u8,
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prec: u8,
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label: u8,
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};
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pub fn localhost(port: u16) Ip6Address {
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return .{
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.bytes = .{ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1 },
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@ -597,6 +654,98 @@ pub const Ip6Address = struct {
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pub fn eql(a: Ip6Address, b: Ip6Address) bool {
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return a.port == b.port and std.mem.eql(u8, &a.bytes, &b.bytes);
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}
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pub fn isMultiCast(a: Ip6Address) bool {
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return a.bytes[0] == 0xff;
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}
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pub fn isLinkLocal(a: Ip6Address) bool {
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const b = &a.bytes;
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return b[0] == 0xfe and (b[1] & 0xc0) == 0x80;
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}
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pub fn isLoopBack(a: Ip6Address) bool {
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const b = &a.bytes;
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return b[0] == 0 and b[1] == 0 and
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b[2] == 0 and
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b[12] == 0 and b[13] == 0 and
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b[14] == 0 and b[15] == 1;
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}
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pub fn isSiteLocal(a: Ip6Address) bool {
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const b = &a.bytes;
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return b[0] == 0xfe and (b[1] & 0xc0) == 0xc0;
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}
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pub fn policy(a: Ip6Address) *const Policy {
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const b = &a.bytes;
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for (&defined_policies) |*p| {
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if (!std.mem.eql(u8, b[0..p.len], p.addr[0..p.len])) continue;
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if ((b[p.len] & p.mask) != p.addr[p.len]) continue;
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return p;
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}
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unreachable;
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}
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pub fn scope(a: Ip6Address) u8 {
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if (isMultiCast(a)) return a.bytes[1] & 15;
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if (isLinkLocal(a)) return 2;
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if (isLoopBack(a)) return 2;
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if (isSiteLocal(a)) return 5;
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return 14;
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}
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const defined_policies = [_]Policy{
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.{
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.addr = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01".*,
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.len = 15,
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.mask = 0xff,
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.prec = 50,
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.label = 0,
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},
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.{
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.addr = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xff\xff\x00\x00\x00\x00".*,
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.len = 11,
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.mask = 0xff,
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.prec = 35,
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.label = 4,
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},
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.{
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.addr = "\x20\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00".*,
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.len = 1,
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.mask = 0xff,
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.prec = 30,
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.label = 2,
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},
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.{
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.addr = "\x20\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00".*,
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.len = 3,
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.mask = 0xff,
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.prec = 5,
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.label = 5,
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},
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.{
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.addr = "\xfc\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00".*,
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.len = 0,
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.mask = 0xfe,
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.prec = 3,
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.label = 13,
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},
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// These are deprecated and/or returned to the address
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// pool, so despite the RFC, treating them as special
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// is probably wrong.
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// { "", 11, 0xff, 1, 3 },
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// { "\xfe\xc0", 1, 0xc0, 1, 11 },
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// { "\x3f\xfe", 1, 0xff, 1, 12 },
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// Last rule must match all addresses to stop loop.
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.{
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.addr = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00".*,
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.len = 0,
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.mask = 0,
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.prec = 40,
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.label = 1,
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},
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};
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};
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pub const Stream = struct {
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