AK: Introduce IPAddressCidr datatype #25006

famfo · 2024-09-09T17:55:42Z

This commit introduces a CIDR datatype which will become handy especially for IPv6 to not have to deal with netmasks.

kleinesfilmroellchen

(note to other reviewers: this is part of SIP6TF, so I was consulted on quite a bit of this code and may be biased)

Very nice work, and extensive tests, I like it. I'm not happy with the name though, so some bikeshedding may be required.

AK/IpAddressCidr.h

kleinesfilmroellchen · 2024-09-09T18:16:20Z

AK/IpAddressCidr.h

+    constexpr IPv6Address first_address_of_subnet() const
+    {
+        u8 address[16];
+        u8 free_bits = MAX_LENGTH - length();
+
+        if (free_bits != 128) {
+            u128 mask = NumericLimits<u128>::max() >> free_bits;
+            u8 address_mask[16];
+
+            memcpy(address_mask, &mask, sizeof(address_mask));
+
+            auto const* original_address = ip_address().to_in6_addr_t();
+            for (int i = 0; i < 16; i++) {
+                address[i] = original_address[i] & address_mask[i];
+            }
+        }
+
+        return address;
+    }


This is basically the same algorithm we have for the IPv6 address subnet logic I introduced recently. Do you want to reuse the algorithm nico suggested there (since it's quite a bit more concise)? It should also be constexpr capable.

kleinesfilmroellchen · 2024-09-09T18:16:51Z

AK/IpAddressCidr.h

+    constexpr IPv6Address last_address_of_subnet() const
+    {
+        u8 inverse_address_mask[16];
+        u8 address[16] = { 0 };
+        u8 free_bits = MAX_LENGTH - length();
+        u128 inverse_mask = NumericLimits<u128>::max();
+
+        if (free_bits != 128) {
+            u8 address_mask[16];
+            u128 mask = NumericLimits<u128>::max() >> free_bits;
+            inverse_mask = inverse_mask << (128 - free_bits);
+
+            memcpy(address_mask, &mask, sizeof(address_mask));
+
+            auto const* original_address = ip_address().to_in6_addr_t();
+            for (int i = 0; i < 16; i++) {
+                address[i] = original_address[i] & address_mask[i];
+            }
+        }


Same thing here, I think the other algorithm can be adopted to fill one bits instead of zero bits.

AK/IpAddressCidr.h

Hendiadyoin1

Mainly Nits on my end, that would likely need support from other places in the code base to resolve

Hendiadyoin1 · 2024-09-10T08:27:10Z

AK/IpAddressCidr.h

I'd prefer CIDR

AK/IpAddressCidr.h

Hendiadyoin1 · 2024-09-10T08:36:06Z

AK/IpAddressCidr.h

+        auto address_string = TRY(m_address.to_string());
+
+#ifdef KERNEL
+        TRY(builder.try_append(address_string->view()));
+#else
+        TRY(builder.try_append(address_string));
+#endif
+
+        TRY(builder.try_append('/'));
+        TRY(builder.try_appendff("{}", m_length));


Ideally this would just be a

#ifdef KERNEL return KSting::formatted("{}/{}", m_address, m_length()); #else return Sting::try_formatted("{}/{}", m_address, m_length()); #endif

but we're likely missing a custom formatter, are we?
Note that fallibility in the Userland case is not enforced (anymore)

Just doing

#ifdef KERNEL ErrorOr<NonnullOwnPtr<Kernel::KString>> to_string() const { return KString::formatted("{}/{}", m_address, m_length); } #else ErrorOr<String> to_string() const { return String::formatted("{}/{}", m_address, m_length); } #endif

works is this case both for IPv4 and IPv6 in hosts and serenity tests. I'll adopt this for formatting.

AK/IpAddressCidr.h

Hendiadyoin1 · 2024-09-10T08:48:28Z

AK/IpAddressCidr.h

+        u32 mask = netmask().to_u32();
+        u32 first = ip_address().to_u32() & mask;
+        return IPv4Address(first | ~mask);


Nit:
Isn't this essentially

ip_address().to_u32() | ((1<<m_length) - 1)

But might be mistaken bc of endianness

The entire IPv4 address is stored in reverse host endianness so this won't work like this:

Running test 'should_find_last_in_subnet'. FAIL: TestIPv4AddressCidr.cpp:44: EXPECT_EQ(address.last_address_of_subnet(), IPv4Address(192, 0, 2, 255)) failed with lhs=255.255.255.1 and rhs=192.0.2.255

AK/IpAddressCidr.h

Hendiadyoin1 · 2024-09-10T08:58:27Z

AK/IpAddressCidr.h

+        if (free_bits != 128) {
+            NetworkOrdered<u128> mask = NumericLimits<u128>::max() << free_bits;
+            auto address_mask = bit_cast<Array<u8, 16>>(mask);
+
+            auto const* original_address = ip_address().to_in6_addr_t();
+            for (int i = 0; i < 16; i++) {
+                address[i] = original_address[i] & address_mask[i];
+            }
+        }
+
+        auto inverse_address_mask = bit_cast<Array<u8, 16>>(inverse_mask);
+
+        for (int i = 0; i < 16; i++) {
+            address[i] = address[i] | inverse_address_mask[i];
+        }
+
+        return address;


See above/V4 version

AK/IpAddressCidr.h

Hendiadyoin1 · 2024-09-10T09:01:53Z

AK/IpAddressCidr.h

+template<>
+struct Formatter<IPv6AddressCidr> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, IPv6AddressCidr value)
+    {
+        return Formatter<StringView>::format(builder, TRY(value.to_string())->view());
+    }
+};
+#else
+template<>
+struct Formatter<IPv6AddressCidr> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, IPv6AddressCidr value)
+    {
+        return Formatter<StringView>::format(builder, TRY(value.to_string()));
+    }
+};


See the OG commit

What I meant with this, is that this could mirror the actual implementation of the CIDR to_string method,
maybe even replace it.

With some template shenanigans (Ie DerivedFrom<IpAddressCIDR>) all formatters could use the same code

Hendiadyoin1 · 2024-09-10T09:02:11Z

AK/IpAddressCidr.h

+template<>
+struct Formatter<IPv4AddressCidr> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, IPv4AddressCidr value)
+    {
+        return Formatter<StringView>::format(builder, TRY(value.to_string())->view());
+    }
+};
+#else
+template<>
+struct Formatter<IPv4AddressCidr> : Formatter<StringView> {
+    ErrorOr<void> format(FormatBuilder& builder, IPv4AddressCidr value)
+    {
+        return Formatter<StringView>::format(builder, TRY(value.to_string()));
+    }
+};


See OG commit

BuggieBot · 2024-09-10T13:49:43Z

Hello!

One or more of the commit messages in this PR do not match the SerenityOS code submission policy, please check the lint_commits CI job for more details on which commits were flagged and why.
Please do not close this PR and open another, instead modify your commit message(s) with git commit --amend and force push those changes to update this PR.

famfo · 2024-09-10T13:51:05Z

I will squash this again later when the code itself is fine

github-actions bot added the 👀 pr-needs-review PR needs review from a maintainer or community member label Sep 9, 2024

kleinesfilmroellchen suggested changes Sep 9, 2024

View reviewed changes

famfo added 3 commits September 10, 2024 00:59

AK: Add IPAddressCidr datatype

0ee7daa

AK/IpAddressCidr: Add IPv4AddressCidr

1103339

AK/IpAddressCidr: Add IPv6AddressCidr

695a66a

famfo force-pushed the IPAddressCidr branch from 3329767 to 695a66a Compare September 9, 2024 23:08

Hendiadyoin1 reviewed Sep 10, 2024

View reviewed changes

famfo added 3 commits September 10, 2024 15:43

fixup! Base: use more auto, change fromatting

76bfe74

fixup! IPv4: move MAX_LENGTH to the top

bcf16e1

fixup! IPv6: move MAX_LENGTH to top, return IPv6Address explicitly

203e4bf

famfo added 2 commits September 11, 2024 01:17

fixup: Base: use release_value

b754b80

fixup: IPv6: use release_value

5b792e9

famfo marked this pull request as draft September 10, 2024 23:25

github-actions bot removed the 👀 pr-needs-review PR needs review from a maintainer or community member label Sep 10, 2024

famfo added 2 commits September 13, 2024 03:29

AK/IPv6Address: Add to and from u128 functions

074cf8a

fixup: IPv6: use u128 datatypes

06fea38

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AK: Introduce IPAddressCidr datatype #25006

AK: Introduce IPAddressCidr datatype #25006

famfo commented Sep 9, 2024

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kleinesfilmroellchen Sep 9, 2024

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famfo Sep 10, 2024 •

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famfo commented Sep 10, 2024

AK: Introduce IPAddressCidr datatype #25006

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AK: Introduce IPAddressCidr datatype #25006

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BuggieBot commented Sep 10, 2024

famfo commented Sep 10, 2024

famfo Sep 10, 2024 •

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