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authorDavide Caratti <dcaratti@redhat.com>2020-10-15 18:39:27 +0200
committerJakub Kicinski <kuba@kernel.org>2020-10-15 11:45:19 -0700
commit346e320cb2103edef709c4466a29140c4a8e527a (patch)
tree405af21ad80b77a0bfda44fa68bbf92051c9c979 /net
parent54086c5a7f159749bc521706bae329cbce3971e9 (diff)
netfilter: nftables: allow re-computing sctp CRC-32C in 'payload' statements
nftables payload statements are used to mangle SCTP headers, but they can only replace the Internet Checksum. As a consequence, nftables rules that mangle sport/dport/vtag in SCTP headers potentially generate packets that are discarded by the receiver, unless the CRC-32C is "offloaded" (e.g the rule mangles a skb having 'ip_summed' equal to 'CHECKSUM_PARTIAL'. Fix this extending uAPI definitions and L4 checksum update function, in a way that userspace programs (e.g. nft) can instruct the kernel to compute CRC-32C in SCTP headers. Also ensure that LIBCRC32C is built if NF_TABLES is 'y' or 'm' in the kernel build configuration. Signed-off-by: Davide Caratti <dcaratti@redhat.com> Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
-rw-r--r--net/netfilter/Kconfig1
-rw-r--r--net/netfilter/nft_payload.c28
2 files changed, 29 insertions, 0 deletions
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index 25313c29d799..52370211e46b 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -441,6 +441,7 @@ endif # NF_CONNTRACK
config NF_TABLES
select NETFILTER_NETLINK
+ select LIBCRC32C
tristate "Netfilter nf_tables support"
help
nftables is the new packet classification framework that intends to
diff --git a/net/netfilter/nft_payload.c b/net/netfilter/nft_payload.c
index 7a2e59638499..dcd3c7b8a367 100644
--- a/net/netfilter/nft_payload.c
+++ b/net/netfilter/nft_payload.c
@@ -22,6 +22,7 @@
#include <linux/icmpv6.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
+#include <net/sctp/checksum.h>
static bool nft_payload_rebuild_vlan_hdr(const struct sk_buff *skb, int mac_off,
struct vlan_ethhdr *veth)
@@ -484,6 +485,19 @@ static int nft_payload_l4csum_offset(const struct nft_pktinfo *pkt,
return 0;
}
+static int nft_payload_csum_sctp(struct sk_buff *skb, int offset)
+{
+ struct sctphdr *sh;
+
+ if (skb_ensure_writable(skb, offset + sizeof(*sh)))
+ return -1;
+
+ sh = (struct sctphdr *)(skb->data + offset);
+ sh->checksum = sctp_compute_cksum(skb, offset);
+ skb->ip_summed = CHECKSUM_UNNECESSARY;
+ return 0;
+}
+
static int nft_payload_l4csum_update(const struct nft_pktinfo *pkt,
struct sk_buff *skb,
__wsum fsum, __wsum tsum)
@@ -587,6 +601,13 @@ static void nft_payload_set_eval(const struct nft_expr *expr,
skb_store_bits(skb, offset, src, priv->len) < 0)
goto err;
+ if (priv->csum_type == NFT_PAYLOAD_CSUM_SCTP &&
+ pkt->tprot == IPPROTO_SCTP &&
+ skb->ip_summed != CHECKSUM_PARTIAL) {
+ if (nft_payload_csum_sctp(skb, pkt->xt.thoff))
+ goto err;
+ }
+
return;
err:
regs->verdict.code = NFT_BREAK;
@@ -623,6 +644,13 @@ static int nft_payload_set_init(const struct nft_ctx *ctx,
case NFT_PAYLOAD_CSUM_NONE:
case NFT_PAYLOAD_CSUM_INET:
break;
+ case NFT_PAYLOAD_CSUM_SCTP:
+ if (priv->base != NFT_PAYLOAD_TRANSPORT_HEADER)
+ return -EINVAL;
+
+ if (priv->csum_offset != offsetof(struct sctphdr, checksum))
+ return -EINVAL;
+ break;
default:
return -EOPNOTSUPP;
}