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From 5ba6bb92b9ec3545d86d598f07643c399a47c7ad Mon Sep 17 00:00:00 2001
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From: Phil Sutter <phil@nwl.cc>
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Date: Tue, 12 Feb 2019 22:51:34 +0100
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Subject: [PATCH] Print IPv6 prefixes in CIDR notation
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According to RFC4291, IPv6 prefixes are represented in CIDR notation.
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While the use of a "netmask" notation is not explicitly denied, its
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existence merely stems from applying IPv4 standards to IPv6. This is not
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necessarily correct.
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Therefore change printing of IPv6 prefixes to use CIDR notation as long
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as the address mask's bits are left contiguous.
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Signed-off-by: Phil Sutter <phil@nwl.cc>
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Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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Signed-off-by: Phil Sutter <psutter@redhat.com>
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---
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useful_functions.c | 35 ++++++++++++++++++++++++++++++-----
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1 file changed, 30 insertions(+), 5 deletions(-)
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diff --git a/useful_functions.c b/useful_functions.c
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index 8a34f820f230b..bf4393712fa44 100644
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--- a/useful_functions.c
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+++ b/useful_functions.c
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@@ -416,16 +416,41 @@ char *ebt_ip6_to_numeric(const struct in6_addr *addrp)
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return (char *)inet_ntop(AF_INET6, addrp, buf, sizeof(buf));
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}
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+int ebt_ip6mask_to_cidr(const struct in6_addr *k)
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+{
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+ unsigned int bits = 0;
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+ uint32_t a, b, c, d;
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+
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+ a = ntohl(k->s6_addr32[0]);
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+ b = ntohl(k->s6_addr32[1]);
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+ c = ntohl(k->s6_addr32[2]);
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+ d = ntohl(k->s6_addr32[3]);
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+ while (a & 0x80000000U) {
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+ ++bits;
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+ a <<= 1;
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+ a |= (b >> 31) & 1;
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+ b <<= 1;
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+ b |= (c >> 31) & 1;
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+ c <<= 1;
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+ c |= (d >> 31) & 1;
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+ d <<= 1;
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+ }
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+ if (a != 0 || b != 0 || c != 0 || d != 0)
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+ return -1;
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+ return bits;
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+}
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+
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char *ebt_ip6_mask_to_string(const struct in6_addr *msk)
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{
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- /* /0000:0000:0000:0000:0000:000.000.000.000
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- * /0000:0000:0000:0000:0000:0000:0000:0000 */
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+ int l = ebt_ip6mask_to_cidr(msk);
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static char buf[51+1];
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- if (msk->s6_addr32[0] == 0xFFFFFFFFL && msk->s6_addr32[1] == 0xFFFFFFFFL &&
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- msk->s6_addr32[2] == 0xFFFFFFFFL && msk->s6_addr32[3] == 0xFFFFFFFFL)
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+
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+ if (l == 127)
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*buf = '\0';
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- else
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+ else if (l == -1)
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sprintf(buf, "/%s", ebt_ip6_to_numeric(msk));
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+ else
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+ sprintf(buf, "/%d", l);
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return buf;
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}
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--
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2.21.0
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