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[dns] fix and simplify OPT record reuse of TTL field (#6187)

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This commit fixes and simplifies the `OptRecord` implementation. The
OPT RR re-purposes the existing TTL field (which is a `uint32_t`) and
uses it for Extended Response Code (`uint8_t`), Version (`uint8_t`),
and flags. The new implementation treats the `mTtl` as a byte array
and directly reads/writes bytes at different indexes corresponding to
different re-purposed data fields. This ensures that the fields are
encoded correctly independent of the endianness of the platform.
This commit is contained in:
Abtin Keshavarzian
2021-02-23 13:10:36 -08:00
committed by GitHub
parent f57c5e2370
commit 78c0c4e573
1 changed files with 17 additions and 26 deletions
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src/core/net/dns_types.hpp
+17 -26
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@@ -2279,7 +2279,7 @@ private:
} OT_TOOL_PACKED_END;
/**
* This class implements DNS OPT Pseudo Resource Record header for EDNS(0) (RFC 6981 - Section 6.1).
* This class implements DNS OPT Pseudo Resource Record header for EDNS(0) (RFC 6891 - Section 6.1).
*
*/
OT_TOOL_PACKED_BEGIN
@@ -2332,10 +2332,7 @@ public:
* @return The upper 8-bit of the extended 12-bit Response Code.
*
*/
uint8_t GetExtendedResponseCode(void) const
{
return static_cast<uint8_t>((mTtl & kExtRCodeMask) >> kExtRCodeffset);
}
uint8_t GetExtendedResponseCode(void) const { return GetTtlByteAt(kExtRCodeByteIndex); }
/**
* This method sets the upper 8-bit of the extended 12-bit Response Code.
@@ -2345,11 +2342,7 @@ public:
* @param[in] aExtendedResponse The upper 8-bit of the extended 12-bit Response Code.
*
*/
void SetExtnededResponseCode(uint8_t aExtendedResponse)
{
mTtl &= ~kExtRCodeffset;
mTtl |= (static_cast<uint32_t>(aExtendedResponse) << kExtRCodeffset);
}
void SetExtnededResponseCode(uint8_t aExtendedResponse) { GetTtlByteAt(kExtRCodeByteIndex) = aExtendedResponse; }
/**
* This method gets the Version field.
@@ -2357,7 +2350,7 @@ public:
* @returns The version.
*
*/
uint8_t GetVersion(void) const { return static_cast<uint8_t>((mTtl & kVersionMask) >> kVersionOffset); }
uint8_t GetVersion(void) const { return GetTtlByteAt(kVersionByteIndex); }
/**
* This method set the Version field.
@@ -2365,11 +2358,7 @@ public:
* @param[in] aVersion The version.
*
*/
void SetVersion(uint8_t aVersion)
{
mTtl &= ~kVersionMask;
mTtl |= (static_cast<uint32_t>(aVersion) << kVersionOffset);
}
void SetVersion(uint8_t aVersion) { GetTtlByteAt(kVersionByteIndex) = aVersion; }
/**
* This method indicates whether the DNSSEC OK flag is set or not.
@@ -2377,19 +2366,19 @@ public:
* @returns True if DNSSEC OK flag is set in the header, false otherwise.
*
*/
bool IsDnsSecurityFlagSet(void) const { return (mTtl & kDnsSecFlag) != 0; }
bool IsDnsSecurityFlagSet(void) const { return (GetTtlByteAt(kFlagByteIndex) & kDnsSecFlag) != 0; }
/**
* This method clears the DNSSEC OK bit flag.
*
*/
void ClearDnsSecurityFlag(void) { mTtl &= ~kDnsSecFlag; }
void ClearDnsSecurityFlag(void) { GetTtlByteAt(kFlagByteIndex) &= ~kDnsSecFlag; }
/**
* This method sets the DNSSEC OK bit flag.
*
*/
void SetDnsSecurityFlag(void) { mTtl |= kDnsSecFlag; }
void SetDnsSecurityFlag(void) { GetTtlByteAt(kFlagByteIndex) |= kDnsSecFlag; }
private:
// The OPT RR re-purposes the existing CLASS and TTL fields in the
@@ -2401,20 +2390,22 @@ private:
// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
// | EXTENDED-RCODE | VERSION |
// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
// | DO| Z |
// | DO| Z | Z |
// +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
//
// The variable data part of OPT RR can contain zero of more `Option`.
enum : uint32_t
enum : uint8_t
{
kExtRCodeffset = 24, // Extended RCODE field offset.
kExtRCodeMask = 0xf << kExtRCodeffset, // Extended RCODE field mask.
kVersionOffset = 16, // Version field offset.
kVersionMask = 0xf << kVersionOffset, // Version field mask.
kDnsSecFlag = 1 << 15, // DnsSec bit flag.
kExtRCodeByteIndex = 0, // Byte index of Extended RCODE within the TTL field.
kVersionByteIndex = 1, // Byte index of Version within the TTL field.
kFlagByteIndex = 2, // Byte index of flag byte within the TTL field.
kDnsSecFlag = 1 << 7, // DNSSec OK bit flag.
};
uint8_t GetTtlByteAt(uint8_t aIndex) const { return reinterpret_cast<const uint8_t *>(&mTtl)[aIndex]; }
uint8_t &GetTtlByteAt(uint8_t aIndex) { return reinterpret_cast<uint8_t *>(&mTtl)[aIndex]; }
} OT_TOOL_PACKED_END;
/**