EffectiveMss

netstack3_base

Struct EffectiveMss 

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pub struct EffectiveMss { /* private fields */ }
Expand description

Like Mss, but smaller to account for fixed-size TCP Options.

This corresponds to the “effective send MSS” as defined in RFC 9293 section 3.7.1: Eff.snd.MSS = min(SendMSS+20, MMS_S) - TCPhdrsize - IPoptionsize where: […] * TCPhdrsize is the size of the fixed TCP header and any options.

Both Mss and EffectiveMss have their place in TCP. For example, the TCP MSS option has Mss semantics, while the MSS used to calculate receive windows & congestion windows has EffectiveMss semantics. When implementing a TCP feature, refer to the feature’s RFC to determine which MSS semantics are appropriate to use.

Note: this implementation accounts for all fixed-sized TCP Options that are part of SegmentOptions. SACK blocks are ignored, because they are variable sized. Variable sized options pose a problem when calculating the EffectiveMss because they vary from segment to segment, whereas the EffectiveMss should be stable throughout the lifetime of the connection. While, no RFC explicitly states how to account for variable sized options, we take inspiration from Linux’s TCP implementation and choose to ignore them until it comes time to actually calculate payload sizes for a given segment.

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impl EffectiveMss

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pub const fn from_mss(mss: Mss, timestamp_option_enabled: bool) -> Self

Constructs an EffectiveMss from an Mss

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pub fn payload_size(&self, options: &SegmentOptions) -> NonZeroU16

Computes the amount of payload data to include in a segment.

Accounts for the size of any variable-sized options present in the segment.

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pub fn mss(&self) -> &Mss

Returns the original Mss used to compute this EffectiveMss.

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pub fn update_mss(&mut self, new: Mss)

Replaces the held Mss with a new value.

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pub const fn get(&self) -> u16

Gets the numeric value of the MSS.

Trait Implementations§

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impl Clone for EffectiveMss

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fn clone(&self) -> EffectiveMss

Returns a duplicate of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for EffectiveMss

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl From<EffectiveMss> for u32

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fn from(mss: EffectiveMss) -> Self

Converts to this type from the input type.
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impl From<EffectiveMss> for usize

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fn from(mss: EffectiveMss) -> Self

Converts to this type from the input type.
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impl PartialEq for EffectiveMss

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fn eq(&self, other: &EffectiveMss) -> bool

Tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl Copy for EffectiveMss

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impl Eq for EffectiveMss

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impl StructuralPartialEq for EffectiveMss

Auto Trait Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (clone_to_uninit)
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fn __clone_box(&self, _: Private) -> *mut ()

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impl<T, D> Encode<Ambiguous1, D> for T
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unsafe fn encode( self, _encoder: &mut Encoder<'_, D>, _offset: usize, _depth: Depth, ) -> Result<(), Error>

Encodes the object into the encoder’s buffers. Any handles stored in the object are swapped for Handle::INVALID. Read more
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impl<T, D> Encode<Ambiguous2, D> for T
where D: ResourceDialect,

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unsafe fn encode( self, _encoder: &mut Encoder<'_, D>, _offset: usize, _depth: Depth, ) -> Result<(), Error>

Encodes the object into the encoder’s buffers. Any handles stored in the object are swapped for Handle::INVALID. Read more
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fn equivalent(&self, key: &K) -> bool

Compare self to key and return true if they are equal.
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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const ALIGN: usize

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unsafe fn init(init: <T as Pointable>::Init) -> usize

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where B: BufferMut + Debug,

Receive a frame. Read more
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fn send_frame<S>( &mut self, bindings_ctx: &mut BC, metadata: Meta, frame: S, ) -> Result<(), ErrorAndSerializer<SendFrameErrorReason, S>>
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Send a frame. Read more
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fn send_meta<SS>( self, core_ctx: &mut FakeCoreCtx<S, Meta, DeviceId>, bindings_ctx: &mut BC, frame: SS, ) -> Result<(), ErrorAndSerializer<SendFrameErrorReason, SS>>
where SS: Serializer, <SS as Serializer>::Buffer: BufferMut,

Sends this frame metadata to the provided contexts.
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impl<Meta, BC> SendableFrameMeta<FakeFrameCtx<Meta>, BC> for Meta

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fn send_meta<S>( self, core_ctx: &mut FakeFrameCtx<Meta>, _bindings_ctx: &mut BC, frame: S, ) -> Result<(), ErrorAndSerializer<SendFrameErrorReason, S>>
where S: Serializer, <S as Serializer>::Buffer: BufferMut,

Sends this frame metadata to the provided contexts.
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where BC: TimerBindingsTypes, Id: HandleableTimer<CC, BC>,

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fn handle_timer( &mut self, bindings_ctx: &mut BC, dispatch: Id, timer: <BC as TimerBindingsTypes>::UniqueTimerId, )

Handle a timer firing. Read more
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type Error = <U as TryFrom<T>>::Error

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