diff options
| author |   Florian Westphal <fw@strlen.de> | 2018-08-22 11:33:27 +0200 |
|---|---|---|
| committer |   Pablo Neira Ayuso <pablo@netfilter.org> | 2018-08-24 09:58:16 +0200 |
| commit | 10568f6c5761db24249c610c94d6e44d5505a0ba (patch) | |
| tree | ff21dc6e19b014a55c5956bccb7209e19a109535 /net/netfilter/xt_CHECKSUM.c | |
| parent | netfilter: xt_cluster: add dependency on conntrack module (diff) | |
| download | linux-dev-10568f6c5761db24249c610c94d6e44d5505a0ba.tar.xz linux-dev-10568f6c5761db24249c610c94d6e44d5505a0ba.zip | |
netfilter: xt_checksum: ignore gso skbs
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>
Diffstat (limited to 'net/netfilter/xt_CHECKSUM.c')
| -rw-r--r-- | net/netfilter/xt_CHECKSUM.c | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/net/netfilter/xt_CHECKSUM.c b/net/netfilter/xt_CHECKSUM.c index 9f4151ec3e06..6c7aa6a0a0d2 100644 --- a/net/netfilter/xt_CHECKSUM.c +++ b/net/netfilter/xt_CHECKSUM.c @@ -16,6 +16,9 @@ #include <linux/netfilter/x_tables.h> #include <linux/netfilter/xt_CHECKSUM.h> +#include <linux/netfilter_ipv4/ip_tables.h> +#include <linux/netfilter_ipv6/ip6_tables.h> + MODULE_LICENSE("GPL"); MODULE_AUTHOR("Michael S. Tsirkin <mst@redhat.com>"); MODULE_DESCRIPTION("Xtables: checksum modification"); @@ -25,7 +28,7 @@ MODULE_ALIAS("ip6t_CHECKSUM"); static unsigned int checksum_tg(struct sk_buff *skb, const struct xt_action_param *par) { - if (skb->ip_summed == CHECKSUM_PARTIAL) + if (skb->ip_summed == CHECKSUM_PARTIAL && !skb_is_gso(skb)) skb_checksum_help(skb); return XT_CONTINUE; @@ -34,6 +37,8 @@ checksum_tg(struct sk_buff *skb, const struct xt_action_param *par) static int checksum_tg_check(const struct xt_tgchk_param *par) { const struct xt_CHECKSUM_info *einfo = par->targinfo; + const struct ip6t_ip6 *i6 = par->entryinfo; + const struct ipt_ip *i4 = par->entryinfo; if (einfo->operation & ~XT_CHECKSUM_OP_FILL) { pr_info_ratelimited("unsupported CHECKSUM operation %x\n", @@ -43,6 +48,21 @@ static int checksum_tg_check(const struct xt_tgchk_param *par) if (!einfo->operation) return -EINVAL; + switch (par->family) { + case NFPROTO_IPV4: + if (i4->proto == IPPROTO_UDP && + (i4->invflags & XT_INV_PROTO) == 0) + return 0; + break; + case NFPROTO_IPV6: + if ((i6->flags & IP6T_F_PROTO) && + i6->proto == IPPROTO_UDP && + (i6->invflags & XT_INV_PROTO) == 0) + return 0; + break; + } + + pr_warn_once("CHECKSUM should be avoided. If really needed, restrict with \"-p udp\" and only use in OUTPUT\n"); return 0; } |