72 lines
2.7 KiB
Diff
72 lines
2.7 KiB
Diff
From 770bce967cfc9967273d0acfb3ea018fb7b17522 Mon Sep 17 00:00:00 2001
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From: Beniamino Galvani <bgalvani@redhat.com>
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Date: Fri, 27 May 2022 21:16:18 +0100
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Subject: [PATCH] Fix parsing of IPv6 addresses with peer from netlink.
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In the most common case, an IPv6 address doesn't have a peer and the
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IFA_ADDRESS netlink attribute contains the address itself.
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But if the address has a peer (typically for point to point links),
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then IFA_ADDRESS contains the peer address and IFA_LOCAL contains the
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address [1].
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[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/net/ipv6/addrconf.c?h=v5.17#n5030
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Fix the parsing of IPv6 addresses with peers, as currently dnsmasq
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unsuccessfully tries to bind on the peer address.
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A simple reproducer is:
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dnsmasq --conf-file=/dev/null -i dummy1 -d --bind-dynamic &
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sleep 2
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ip link add dummy1 type dummy
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ip link set dummy1 up
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ip addr add dev dummy1 fd01::1/64 peer fd01::2/64
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ip addr add dev dummy1 fd01::42/64
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sleep 2
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ss -lnp | grep dnsmasq | grep fd01
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Before the patch:
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dnsmasq: failed to create listening socket for fd01::2: Cannot assign requested address
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dnsmasq: failed to create listening socket for fd01::2: Cannot assign requested address
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udp UNCONN 0 [fd01::42]:53 [::]:* users:(("dnsmasq",pid=23947,fd=14))
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tcp LISTEN 0 [fd01::42]:53 [::]:* users:(("dnsmasq",pid=23947,fd=15
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After:
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udp UNCONN 0 [fd01::42]:53 [::]:* users:(("dnsmasq",pid=23973,fd=16))
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udp UNCONN 0 [fd01::1]:53 [::]:* users:(("dnsmasq",pid=23973,fd=14))
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tcp LISTEN 0 [fd01::42]:53 [::]:* users:(("dnsmasq",pid=23973,fd=17))
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tcp LISTEN 0 [fd01::1]:53 [::]:* users:(("dnsmasq",pid=23973,fd=15))
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Conflict:NA
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Reference:https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commit;h=770bce967cfc9967273d0acfb3ea018fb7b17522
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---
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src/netlink.c | 11 ++++++++++-
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1 file changed, 10 insertions(+), 1 deletion(-)
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diff --git a/src/netlink.c b/src/netlink.c
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index da82943..c156cde 100644
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--- a/src/netlink.c
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+++ b/src/netlink.c
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@@ -258,7 +258,16 @@ int iface_enumerate(int family, void *parm, int (*callback)())
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while (RTA_OK(rta, len1))
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{
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- if (rta->rta_type == IFA_ADDRESS)
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+ /*
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+ * Important comment: (from if_addr.h)
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+ * IFA_ADDRESS is prefix address, rather than local interface address.
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+ * It makes no difference for normally configured broadcast interfaces,
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+ * but for point-to-point IFA_ADDRESS is DESTINATION address,
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+ * local address is supplied in IFA_LOCAL attribute.
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+ */
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+ if (rta->rta_type == IFA_LOCAL)
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+ addrp = ((struct in6_addr *)(rta+1));
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+ else if (rta->rta_type == IFA_ADDRESS && !addrp)
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addrp = ((struct in6_addr *)(rta+1));
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else if (rta->rta_type == IFA_CACHEINFO)
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{
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--
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2.23.0
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