passt/ip.h, branch 2026_05_07.1afd4ed

ip: Prepare ip.[ch] for sharing with pesto tool

2026-05-07T06:06:30+00:00

Most things in ip.[ch] related purely to IP addresses and headers with
no dependency on other passt/pasta internals.  A number of these will be
useful to re-use in pesto.  The exception is ipv6_l4hdr() which uses
iov_tail.

The only caller of this is in tap.c, so move the function there.  Along
with moving the constant byteswapping functions to common.h, that lets
ip.[ch] to be linked into pesto as well as passt/pasta.

Signed-off-by: David Gibson 
Reviewed-by: Laurent Vivier 
[sbrivio: Dropped duplicate definition of __bswap_constant_32() while
 at it, reported by Laurent]
Signed-off-by: Stefano Brivio

ip: Define a bound for the string returned by ipproto_name()

2026-03-28T13:36:01+00:00

ipproto_name() returns a static string of theoretically unbounded length.
That's going to be inconvenient in future, so introduce IPPROTO_STRLEN
giving an explicit bound on the length.  Use static_assert() and some
macros to ensure nothing we return can exceed this.

Signed-off-by: David Gibson 
Signed-off-by: Stefano Brivio

Add missing includes to headers

2026-03-04T16:39:57+00:00

Support build systems like bazel that check that headers are
self-contained.

Also update includes so that clang-include-cleaner succeeds.

Tested with:
clang-include-cleaner-19 --extra-arg=-D_GNU_SOURCE --extra-arg=-DPAGE_SIZE=4096 --extra-arg=-DVERSION=\"git\" --extra-arg=-DHAS_GETRANDOM *.h *.c

Signed-off-by: Peter Foley 
Signed-off-by: Stefano Brivio

conf: Support CIDR notation for -a/--address option

2026-02-24T11:05:53+00:00

We extend the -a/--address option to accept addresses in CIDR notation
(e.g., 192.168.1.1/24 or 2001:db8::1/64) as an alternative to using
separate -a and -n options.

We add a new inany_prefix_pton() helper function that:
- Parses address strings with a compulsory /prefix_len suffix
- Validates prefix length based on address family (0-32 for IPv4,
  0-128 for IPv6), including handling of IPv4-to-IPv6 mapping case.

For IPv4, the prefix length is stored in ip4.prefix_len when provided.
For IPv6, the given prefix length is still overridden by the default
value 64

Mixing -n and CIDR notation results in an error to catch likely user
mistakes.

Also fix a bug in conf_ip4_prefix() that was incorrectly using the
global 'optarg' instead of its 'arg' parameter.

Signed-off-by: Jon Maloy 
[sbrivio: Fix merge conflict with commit 0c611bcd3120]
Signed-off-by: Stefano Brivio

ip: Add ipproto_name() function

2026-01-18T11:47:44+00:00

Add a function to get the name of an IP protocol from its number.  Usually
this would be done by getprotobynumber(), but that requires access to
/etc/protocols and might allocate.  We can't do either of those once we've
self-isolated.

Signed-off-by: David Gibson 
Reviewed-by: Laurent Vivier 
Signed-off-by: Stefano Brivio

ip: Use iov_tail in ipv6_l4hdr()

2025-09-03T18:43:31+00:00

Use packet_data() and extract headers using IOV_REMOVE_HEADER()
and IOV_PEEK_HEADER() rather than packet_get().

Signed-off-by: Laurent Vivier 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio

codespell: Correct typos in comments and error message

2025-05-15T16:06:30+00:00

This commit addresses several spelling errors identified by the `codespell`
tool. The corrections apply to:
- Code comments in `fwd.c`, `ip.h`, `isolation.c`, and `log.c`.
- An error message string in `vhost_user.c`.

Specifically, the following misspellings were corrected:
- "adddress" to "address"
- "capabilites" to "capabilities"
- "Musn't" to "Mustn't"
- "calculatd" to "calculated"
- "Invalide" to "Invalid"

Signed-off-by: Laurent Vivier 
Signed-off-by: Stefano Brivio

conf: Be more precise about minimum MTUs

2025-03-06T19:17:23+00:00

Currently we reject the -m option if given a value less than ETH_MIN_MTU
(68).  That define is derived from the kernel, but its name is misleading:
it doesn't really have anything to do with Ethernet per se, but is rather
the minimum payload any L2 link must be able to handle in order to carry
IPv4.  For IPv6, it's not sufficient: that requires an MTU of at least
1280.

Newer kernels have better named constants IPV4_MIN_MTU and IPv6_MIN_MTU.
Copy and use those constants instead, along with some more specific error
messages.

Signed-off-by: David Gibson 
Signed-off-by: Stefano Brivio

tap: Consider IPv6 flow label when building packet sequences

2025-03-05T20:46:29+00:00

To allow more batching, we group together related packets into "seqs" in
the tap layer, before passing them to the L4 protocol layers.  Currently
we consider the IP protocol, both IP addresses and also the L4 ports when
grouping things into seqs.  We ignore the IPv6 flow label.

We have some future cases where we want to consider the the flow label in
the L4 code, which is awkward if we could be given a single batch with
multiple labels.  Add the flow label to tap6_l4_t and group by it as well
as the other criteria.  In future we could possibly use the flow label
_instead_ of peeking into the L4 header for the ports, but we don't do so
for now.

The guest should use the same flow label for all packets in a low, but if
it doesn't this change won't break anything, it just means we'll batch
things a bit sub-optimally.

Signed-off-by: David Gibson 
Signed-off-by: Stefano Brivio

ip: Helpers to access IPv6 flow label

2025-03-05T20:46:17+00:00

The flow label is a 20-bit field in the IPv6 header.  The length and
alignment make it awkward to pass around as is.  Obviously, it can be
packed into a 32-bit integer though, and we do this in two places.  We
have some further upcoming places where we want to manipulate the flow
label, so make some helpers for marshalling and unmarshalling it to an
integer.

Signed-off-by: David Gibson 
Signed-off-by: Stefano Brivio