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Message-Id: <20220829100121.3821-1-nicolas.dichtel@6wind.com> Date: Mon, 29 Aug 2022 12:01:21 +0200 From: Nicolas Dichtel <nicolas.dichtel@...nd.com> To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>, David Ahern <dsahern@...nel.org> Cc: netdev@...r.kernel.org, Heng Qi <hengqi@...ux.alibaba.com>, Edwin Brossette <edwin.brossette@...nd.com>, kernel test robot <lkp@...el.com>, lkp@...ts.01.org, Nicolas Dichtel <nicolas.dichtel@...nd.com>, stable@...r.kernel.org, kernel test robot <yujie.liu@...el.com> Subject: [PATCH net] ip: fix triggering of 'icmp redirect' __mkroute_input() uses fib_validate_source() to trigger an icmp redirect. My understanding is that fib_validate_source() is used to know if the src address and the gateway address are on the same link. For that, fib_validate_source() returns 1 (same link) or 0 (not the same network). __mkroute_input() is the only user of these positive values, all other callers only look if the returned value is negative. Since the below patch, fib_validate_source() didn't return anymore 1 when both addresses are on the same network, because the route lookup returns RT_SCOPE_LINK instead of RT_SCOPE_HOST. But this is, in fact, right. Let's adapat the test to return 1 again when both addresses are on the same link. CC: stable@...r.kernel.org Fixes: 747c14307214 ("ip: fix dflt addr selection for connected nexthop") Reported-by: kernel test robot <yujie.liu@...el.com> Reported-by: Heng Qi <hengqi@...ux.alibaba.com> Signed-off-by: Nicolas Dichtel <nicolas.dichtel@...nd.com> --- This code exists since more than two decades: https://git.kernel.org/pub/scm/linux/kernel/git/davem/netdev-vger-cvs.git/commit/?id=0c2c94df8133f Please, feel free to comment if my analysis seems wrong. Regards, Nicolas net/ipv4/fib_frontend.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c index f361d3d56be2..943edf4ad4db 100644 --- a/net/ipv4/fib_frontend.c +++ b/net/ipv4/fib_frontend.c @@ -389,7 +389,7 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst, dev_match = dev_match || (res.type == RTN_LOCAL && dev == net->loopback_dev); if (dev_match) { - ret = FIB_RES_NHC(res)->nhc_scope >= RT_SCOPE_HOST; + ret = FIB_RES_NHC(res)->nhc_scope >= RT_SCOPE_LINK; return ret; } if (no_addr) @@ -401,7 +401,7 @@ static int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst, ret = 0; if (fib_lookup(net, &fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE) == 0) { if (res.type == RTN_UNICAST) - ret = FIB_RES_NHC(res)->nhc_scope >= RT_SCOPE_HOST; + ret = FIB_RES_NHC(res)->nhc_scope >= RT_SCOPE_LINK; } return ret; -- 2.33.0
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