mirror of
https://github.com/brain-hackers/linux-brain.git
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2f3839075a
[ Upstream commit 63137bc5882a1882c553d389fdeeeace86ee1741 ]
Fixes an error causing small packets to get dropped. skb_ensure_writable
expects the second parameter to be a length in the ethernet payload.=20
If we want to write the ethernet header (src, dst), we should pass 0.
Otherwise, packets with small payloads (< ETH_ALEN) will get dropped.
Fixes: c1a8311679 ("netfilter: bridge: convert skb_make_writable to skb_ensure_writable")
Signed-off-by: Timothée COCAULT <timothee.cocault@orange.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
89 lines
2.0 KiB
C
89 lines
2.0 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* ebt_snat
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*
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* Authors:
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* Bart De Schuymer <bdschuym@pandora.be>
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*
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* June, 2002
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*
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*/
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#include <linux/module.h>
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#include <net/sock.h>
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#include <linux/if_arp.h>
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#include <net/arp.h>
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#include <linux/netfilter.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter_bridge/ebtables.h>
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#include <linux/netfilter_bridge/ebt_nat.h>
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static unsigned int
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ebt_snat_tg(struct sk_buff *skb, const struct xt_action_param *par)
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{
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const struct ebt_nat_info *info = par->targinfo;
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if (skb_ensure_writable(skb, 0))
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return EBT_DROP;
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ether_addr_copy(eth_hdr(skb)->h_source, info->mac);
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if (!(info->target & NAT_ARP_BIT) &&
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eth_hdr(skb)->h_proto == htons(ETH_P_ARP)) {
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const struct arphdr *ap;
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struct arphdr _ah;
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ap = skb_header_pointer(skb, 0, sizeof(_ah), &_ah);
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if (ap == NULL)
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return EBT_DROP;
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if (ap->ar_hln != ETH_ALEN)
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goto out;
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if (skb_store_bits(skb, sizeof(_ah), info->mac, ETH_ALEN))
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return EBT_DROP;
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}
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out:
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return info->target | ~EBT_VERDICT_BITS;
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}
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static int ebt_snat_tg_check(const struct xt_tgchk_param *par)
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{
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const struct ebt_nat_info *info = par->targinfo;
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int tmp;
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tmp = info->target | ~EBT_VERDICT_BITS;
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if (BASE_CHAIN && tmp == EBT_RETURN)
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return -EINVAL;
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if (ebt_invalid_target(tmp))
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return -EINVAL;
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tmp = info->target | EBT_VERDICT_BITS;
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if ((tmp & ~NAT_ARP_BIT) != ~NAT_ARP_BIT)
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return -EINVAL;
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return 0;
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}
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static struct xt_target ebt_snat_tg_reg __read_mostly = {
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.name = "snat",
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.revision = 0,
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.family = NFPROTO_BRIDGE,
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.table = "nat",
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.hooks = (1 << NF_BR_NUMHOOKS) | (1 << NF_BR_POST_ROUTING),
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.target = ebt_snat_tg,
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.checkentry = ebt_snat_tg_check,
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.targetsize = sizeof(struct ebt_nat_info),
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.me = THIS_MODULE,
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};
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static int __init ebt_snat_init(void)
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{
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return xt_register_target(&ebt_snat_tg_reg);
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}
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static void __exit ebt_snat_fini(void)
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{
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xt_unregister_target(&ebt_snat_tg_reg);
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}
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module_init(ebt_snat_init);
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module_exit(ebt_snat_fini);
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MODULE_DESCRIPTION("Ebtables: Source MAC address translation");
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MODULE_LICENSE("GPL");
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