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Do not overallocate SocketAddress.Buffer #78860

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merged 7 commits into from
Dec 19, 2022
Merged

Do not overallocate SocketAddress.Buffer #78860

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98a1549
do not overallocate SocketAddress.Buffer
antonfirsov Nov 25, 2022
6815398
make sure CopyAddressSizeIntoBuffer and GetAddressSizeOffset are only…
antonfirsov Nov 25, 2022
7392b08
use sizeof(int), improve comments
antonfirsov Nov 26, 2022
ddb50fc
add 4-byte alignment
antonfirsov Nov 30, 2022
c62917c
improve comments
antonfirsov Nov 30, 2022
6363fe3
always align to IntPtr.Size
antonfirsov Nov 30, 2022
aceb23f
fix typo
antonfirsov Dec 14, 2022
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19 changes: 14 additions & 5 deletions src/libraries/Common/src/System/Net/SocketAddress.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -92,7 +92,13 @@ public SocketAddress(AddressFamily family, int size)
}

InternalSize = size;
Buffer = new byte[(size / IntPtr.Size + 2) * IntPtr.Size];
#if !SYSTEM_NET_PRIMITIVES_DLL && WINDOWS
// WSARecvFrom needs a pinned pointer to the 32bit socket address size: https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsarecvfrom
// Allocate IntPtr.Size extra bytes at the end of Buffer ensuring IntPtr.Size alignment, so we don't need to pin anything else.
// The following formula will extend 'size' to the alignment boundary then add IntPtr.Size more bytes.
size = (size + IntPtr.Size - 1) / IntPtr.Size * IntPtr.Size + IntPtr.Size;
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int Extend(int size) => (size + IntPtr.Size - 1) / IntPtr.Size * IntPtr.Size + IntPtr.Size;

for (int i = 10; i < 30; i++) Console.Write($"{i,2} | ");
Console.WriteLine();
for (int i = 10; i < 30; i++) Console.Write($"{Extend(i),2} | ");

Will print:

10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 |
24 | 24 | 24 | 24 | 24 | 24 | 24 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 40 | 40 | 40 | 40 | 40 |

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Right, the old code did

10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 |
24 | 24 | 24 | 24 | 24 | 24 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 32 | 40 | 40 | 40 | 40 | 40 | 40 |

Sensible address structure would already be aligned IMHO and we really just need to put int on boundary of its size (e.g. 4) and we need to make sure it fits to the buffer. The new code does it and now we do it only for Windows where it is used.

#endif
Buffer = new byte[size];

SocketAddressPal.SetAddressFamily(Buffer, family);
}
Expand Down Expand Up @@ -171,20 +177,23 @@ internal IPEndPoint GetIPEndPoint()
return new IPEndPoint(GetIPAddress(), GetPort());
}

#if !SYSTEM_NET_PRIMITIVES_DLL && WINDOWS
// For ReceiveFrom we need to pin address size, using reserved Buffer space.
internal void CopyAddressSizeIntoBuffer()
{
Buffer[Buffer.Length - IntPtr.Size] = unchecked((byte)(InternalSize));
Buffer[Buffer.Length - IntPtr.Size + 1] = unchecked((byte)(InternalSize >> 8));
Buffer[Buffer.Length - IntPtr.Size + 2] = unchecked((byte)(InternalSize >> 16));
Buffer[Buffer.Length - IntPtr.Size + 3] = unchecked((byte)(InternalSize >> 24));
int addressSizeOffset = GetAddressSizeOffset();
Buffer[addressSizeOffset] = unchecked((byte)(InternalSize));
Buffer[addressSizeOffset + 1] = unchecked((byte)(InternalSize >> 8));
Buffer[addressSizeOffset + 2] = unchecked((byte)(InternalSize >> 16));
Buffer[addressSizeOffset + 3] = unchecked((byte)(InternalSize >> 24));
}

// Can be called after the above method did work.
internal int GetAddressSizeOffset()
{
return Buffer.Length - IntPtr.Size;
}
#endif

public override bool Equals(object? comparand) =>
comparand is SocketAddress other &&
Expand Down