Re: [PATCH 2/2] frontend: Format IPv6 addresses according to RFC 5952

[Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>]

On 05/06/2026 14:33, Tu Dinh wrote:
> Scan for and collapse sequences of consecutive zeroes.
> Do not zero-pad components of the IP address.
> 
> Signed-off-by: Tu Dinh <ngoc-tu.dinh@xxxxxxxxxx>

Tests: https://gist.github.com/dinhngtu/103ac89b5c8f23ed4a61cd538cb8f0da

> ---
>   src/xenvif/frontend.c | 87 ++++++++++++++++++++++++++++++++++++-------
>   1 file changed, 73 insertions(+), 14 deletions(-)
> 
> diff --git a/src/xenvif/frontend.c b/src/xenvif/frontend.c
> index 4afc72a..256b35b 100644
> --- a/src/xenvif/frontend.c
> +++ b/src/xenvif/frontend.c
> @@ -700,22 +700,81 @@ FrontendDumpIPv6Address(
>       _In_ PIPV6_ADDRESS              Address
>       )
>   {
> +    ULONG                           Index;
> +    ULONG                           Count;
> +    ULONG                           ZeroIndex;
> +    ULONG                           ZeroCount;
>       NTSTATUS                        status;
>   
> -    status = XENBUS_STORE(Printf,
> -                          &Frontend->StoreInterface,
> -                          Transaction,
> -                          __FrontendGetPrefix(Frontend),
> -                          Node,
> -                          "%04x:%04x:%04x:%04x:%04x:%04x:%04x:%04x",
> -                          NTOHS(Address->Word[0]),
> -                          NTOHS(Address->Word[1]),
> -                          NTOHS(Address->Word[2]),
> -                          NTOHS(Address->Word[3]),
> -                          NTOHS(Address->Word[4]),
> -                          NTOHS(Address->Word[5]),
> -                          NTOHS(Address->Word[6]),
> -                          NTOHS(Address->Word[7]));
> +    Count = ZeroIndex = ZeroCount = 0;
> +    for (Index = 0; Index < 8; Index++) {
> +        if (Address->Word[Index] == 0)
> +            Count++;
> +        else
> +            Count = 0;
> +
> +        if (Count > ZeroCount) {
> +            if (Count == 1)
> +                ZeroIndex = Index;
> +            ZeroCount = Count;
> +        }
> +    }
> +
> +    if (ZeroCount > 1) {
> +        CHAR                        Parts[8][sizeof(":XXXX")];
> +
> +        for (Index = 0; Index < 8; Index++) {
> +            // Consecutive 0s are collapsed into a single semicolon, so that
> +            // appending :xxxx segments would work naturally.
> +            // Compensate for the missing appended semicolon if the last word
> +            // was also collapsed.
> +            if (Index == ZeroIndex || (Index == 7 &&
> +                                       Index == ZeroIndex + ZeroCount - 1)) {
> +                Parts[Index][0] = ':';
> +                Parts[Index][1] = '\0';
> +            } else if (Index > ZeroIndex && Index < ZeroIndex + ZeroCount) {
> +                Parts[Index][0] = '\0';
> +            } else {
> +                status = RtlStringCchPrintfA(Parts[Index],
> +                                             sizeof(Parts[Index]),
> +                                             Index == 0 ? "%hx" : ":%hx",
> +                                             NTOHS(Address->Word[Index]));
> +                if (!NT_SUCCESS(status))
> +                    return status;
> +            }
> +        }
> +
> +        status = XENBUS_STORE(Printf,
> +                              &Frontend->StoreInterface,
> +                              Transaction,
> +                              __FrontendGetPrefix(Frontend),
> +                              Node,
> +                              "%s%s%s%s%s%s%s%s",
> +                              Parts[0],
> +                              Parts[1],
> +                              Parts[2],
> +                              Parts[3],
> +                              Parts[4],
> +                              Parts[5],
> +                              Parts[6],
> +                              Parts[7]);
> +    } else {
> +        status = XENBUS_STORE(Printf,
> +                              &Frontend->StoreInterface,
> +                              Transaction,
> +                              __FrontendGetPrefix(Frontend),
> +                              Node,
> +                              "%hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx",
> +                              NTOHS(Address->Word[0]),
> +                              NTOHS(Address->Word[1]),
> +                              NTOHS(Address->Word[2]),
> +                              NTOHS(Address->Word[3]),
> +                              NTOHS(Address->Word[4]),
> +                              NTOHS(Address->Word[5]),
> +                              NTOHS(Address->Word[6]),
> +                              NTOHS(Address->Word[7]));
> +    }
> +
>       return status;
>   }
>   



--
Ngoc Tu Dinh | Vates XCP-ng Developer

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