10568f6c57
Satish Patel reports a skb_warn_bad_offload() splat caused by -j CHECKSUM rules: -A POSTROUTING -p tcp -m tcp --sport 80 -j CHECKSUM The CHECKSUM target has never worked with GSO skbs, and the above rule makes no sense as kernel will handle checksum updates on transmit. Unfortunately, there are 3rd party tools that install such rules, so we cannot reject this from the config plane without potential breakage. Amend Kconfig text to clarify that the CHECKSUM target is only useful in virtualized environments, where old dhcp clients that use AF_PACKET used to discard UDP packets with a 'bad' header checksum and add a one-time warning in case such rule isn't restricted to UDP. v2: check IP6T_F_PROTO flag before cmp (Michal Kubecek) Reported-by: Satish Patel <satish.txt@gmail.com> Reported-by: Markos Chandras <markos.chandras@suse.com> Reported-by: Michal Kubecek <mkubecek@suse.cz> Signed-off-by: Florian Westphal <fw@strlen.de> Reviewed-by: Michal Kubecek <mkubecek@suse.cz> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
91 lines
2.3 KiB
C
91 lines
2.3 KiB
C
/* iptables module for the packet checksum mangling
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*
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* (C) 2002 by Harald Welte <laforge@netfilter.org>
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* (C) 2010 Red Hat, Inc.
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*
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* Author: Michael S. Tsirkin <mst@redhat.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/netfilter/x_tables.h>
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#include <linux/netfilter/xt_CHECKSUM.h>
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#include <linux/netfilter_ipv4/ip_tables.h>
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#include <linux/netfilter_ipv6/ip6_tables.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Michael S. Tsirkin <mst@redhat.com>");
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MODULE_DESCRIPTION("Xtables: checksum modification");
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MODULE_ALIAS("ipt_CHECKSUM");
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MODULE_ALIAS("ip6t_CHECKSUM");
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static unsigned int
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checksum_tg(struct sk_buff *skb, const struct xt_action_param *par)
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{
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if (skb->ip_summed == CHECKSUM_PARTIAL && !skb_is_gso(skb))
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skb_checksum_help(skb);
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return XT_CONTINUE;
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}
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static int checksum_tg_check(const struct xt_tgchk_param *par)
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{
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const struct xt_CHECKSUM_info *einfo = par->targinfo;
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const struct ip6t_ip6 *i6 = par->entryinfo;
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const struct ipt_ip *i4 = par->entryinfo;
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if (einfo->operation & ~XT_CHECKSUM_OP_FILL) {
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pr_info_ratelimited("unsupported CHECKSUM operation %x\n",
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einfo->operation);
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return -EINVAL;
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}
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if (!einfo->operation)
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return -EINVAL;
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switch (par->family) {
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case NFPROTO_IPV4:
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if (i4->proto == IPPROTO_UDP &&
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(i4->invflags & XT_INV_PROTO) == 0)
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return 0;
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break;
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case NFPROTO_IPV6:
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if ((i6->flags & IP6T_F_PROTO) &&
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i6->proto == IPPROTO_UDP &&
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(i6->invflags & XT_INV_PROTO) == 0)
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return 0;
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break;
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}
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pr_warn_once("CHECKSUM should be avoided. If really needed, restrict with \"-p udp\" and only use in OUTPUT\n");
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return 0;
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}
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static struct xt_target checksum_tg_reg __read_mostly = {
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.name = "CHECKSUM",
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.family = NFPROTO_UNSPEC,
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.target = checksum_tg,
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.targetsize = sizeof(struct xt_CHECKSUM_info),
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.table = "mangle",
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.checkentry = checksum_tg_check,
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.me = THIS_MODULE,
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};
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static int __init checksum_tg_init(void)
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{
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return xt_register_target(&checksum_tg_reg);
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}
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static void __exit checksum_tg_exit(void)
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{
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xt_unregister_target(&checksum_tg_reg);
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}
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module_init(checksum_tg_init);
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module_exit(checksum_tg_exit);
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