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gnrc/ipv6_auto_subnets: allow to configure minimal prefix length #19656

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merged 3 commits into from
May 23, 2023
Merged

gnrc/ipv6_auto_subnets: allow to configure minimal prefix length #19656

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0ee46e8
core/compiler_hints: add may_be_zero()
benpicco May 23, 2023
9358a44
gnrc/ipv6_auto_subnets: remove superfluous newline
benpicco May 23, 2023
2a76911
gnrc/ipv6_auto_subnets: allow to configure minimal prefix length
benpicco May 22, 2023
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13 changes: 13 additions & 0 deletions core/lib/include/compiler_hints.h
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Original file line number Diff line number Diff line change
Expand Up @@ -181,6 +181,19 @@ extern "C" {
#define assume(cond) assert(cond)
#endif

/**
* @brief Wrapper function to silence "comparison is always false due to limited
* range of data type" type of warning when the warning is caused by a
* preprocessor configuration value that may be zero.
*
* @param[in] n Variable that may be zero
* @return The same variable @p n
*/
static inline unsigned may_be_zero(unsigned n)
{
return n;
}

#ifdef __cplusplus
}
#endif
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14 changes: 13 additions & 1 deletion sys/net/gnrc/routing/ipv6_auto_subnets/gnrc_ipv6_auto_subnets.c
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Original file line number Diff line number Diff line change
@@ -1,4 +1,3 @@

/*
* Copyright (C) 2021 ML!PA Consulting GmbH
*
Expand Down Expand Up @@ -90,6 +89,7 @@
* @author Benjamin Valentin <benjamin.valentin@ml-pa.com>
*/

#include "compiler_hints.h"
#include "net/gnrc/ipv6.h"
#include "net/gnrc/netif.h"
#include "net/gnrc/netif/hdr.h"
Expand Down Expand Up @@ -142,6 +142,14 @@
#define CONFIG_GNRC_IPV6_AUTO_SUBNETS_PREFIX_FIX_LEN (0)
#endif

/**
* @brief Minimal length of a new prefix.
* e.g. Linux will only accept /64 prefixes for SLAAC
*/
#ifndef CONFIG_GNRC_IPV6_AUTO_SUBNETS_PREFIX_MIN_LEN
#define CONFIG_GNRC_IPV6_AUTO_SUBNETS_PREFIX_MIN_LEN (0)
#endif

/**
* @brief Number of subnets that can be configured.
*
Expand Down Expand Up @@ -370,6 +378,10 @@ static void _configure_subnets(uint8_t subnets, uint8_t start_idx, gnrc_netif_t
return;
}

if (new_prefix_len < may_be_zero(CONFIG_GNRC_IPV6_AUTO_SUBNETS_PREFIX_MIN_LEN)) {
new_prefix_len = CONFIG_GNRC_IPV6_AUTO_SUBNETS_PREFIX_MIN_LEN;
}

while ((downstream = gnrc_netif_iter(downstream))) {
gnrc_pktsnip_t *tmp;
ipv6_addr_t new_prefix;
Expand Down