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authorDaniel Borkmann <dborkman@redhat.com>2013-10-30 11:50:52 +0100
committerDavid S. Miller <davem@davemloft.net>2013-11-03 23:04:57 -0500
commite6d8b64b34aa8a9fe39609bc2db8a243b0331ceb (patch)
treede3bbb3dc4e08fd17fcde46aedb239d274e45d6b /include/net
parent2817a336d4d533fb8b68719723cd60ea7dd7c09e (diff)
net: sctp: fix and consolidate SCTP checksumming code
This fixes an outstanding bug found through IPVS, where SCTP packets with skb->data_len > 0 (non-linearized) and empty frag_list, but data accumulated in frags[] member, are forwarded with incorrect checksum letting SCTP initial handshake fail on some systems. Linearizing each SCTP skb in IPVS to prevent that would not be a good solution as this leads to an additional and unnecessary performance penalty on the load-balancer itself for no good reason (as we actually only want to update the checksum, and can do that in a different/better way presented here). The actual problem is elsewhere, namely, that SCTP's checksumming in sctp_compute_cksum() does not take frags[] into account like skb_checksum() does. So while we are fixing this up, we better reuse the existing code that we have anyway in __skb_checksum() and use it for walking through the data doing checksumming. This will not only fix this issue, but also consolidates some SCTP code with core sk_buff code, bringing it closer together and removing respectively avoiding reimplementation of skb_checksum() for no good reason. As crc32c() can use hardware implementation within the crypto layer, we leave that intact (it wraps around / falls back to e.g. slice-by-8 algorithm in __crc32c_le() otherwise); plus use the __crc32c_le_combine() combinator for crc32c blocks. Also, we remove all other SCTP checksumming code, so that we only have to use sctp_compute_cksum() from now on; for doing that, we need to transform SCTP checkumming in output path slightly, and can leave the rest intact. Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/net')
-rw-r--r--include/net/sctp/checksum.h56
1 files changed, 19 insertions, 37 deletions
diff --git a/include/net/sctp/checksum.h b/include/net/sctp/checksum.h
index 259924d63ba6..6bd44fe94c26 100644
--- a/include/net/sctp/checksum.h
+++ b/include/net/sctp/checksum.h
@@ -42,56 +42,38 @@
#include <linux/types.h>
#include <net/sctp/sctp.h>
#include <linux/crc32c.h>
+#include <linux/crc32.h>
-static inline __u32 sctp_crc32c(__u32 crc, u8 *buffer, u16 length)
+static inline __wsum sctp_csum_update(const void *buff, int len, __wsum sum)
{
- return crc32c(crc, buffer, length);
-}
-
-static inline __u32 sctp_start_cksum(__u8 *buffer, __u16 length)
-{
- __u32 crc = ~(__u32)0;
- __u8 zero[sizeof(__u32)] = {0};
-
- /* Optimize this routine to be SCTP specific, knowing how
- * to skip the checksum field of the SCTP header.
+ /* This uses the crypto implementation of crc32c, which is either
+ * implemented w/ hardware support or resolves to __crc32c_le().
*/
-
- /* Calculate CRC up to the checksum. */
- crc = sctp_crc32c(crc, buffer, sizeof(struct sctphdr) - sizeof(__u32));
-
- /* Skip checksum field of the header. */
- crc = sctp_crc32c(crc, zero, sizeof(__u32));
-
- /* Calculate the rest of the CRC. */
- crc = sctp_crc32c(crc, &buffer[sizeof(struct sctphdr)],
- length - sizeof(struct sctphdr));
- return crc;
-}
-
-static inline __u32 sctp_update_cksum(__u8 *buffer, __u16 length, __u32 crc32)
-{
- return sctp_crc32c(crc32, buffer, length);
+ return crc32c(sum, buff, len);
}
-static inline __le32 sctp_end_cksum(__u32 crc32)
+static inline __wsum sctp_csum_combine(__wsum csum, __wsum csum2,
+ int offset, int len)
{
- return cpu_to_le32(~crc32);
+ return __crc32c_le_combine(csum, csum2, len);
}
-/* Calculate the CRC32C checksum of an SCTP packet. */
static inline __le32 sctp_compute_cksum(const struct sk_buff *skb,
unsigned int offset)
{
- const struct sk_buff *iter;
+ struct sctphdr *sh = sctp_hdr(skb);
+ __le32 ret, old = sh->checksum;
+ const struct skb_checksum_ops ops = {
+ .update = sctp_csum_update,
+ .combine = sctp_csum_combine,
+ };
- __u32 crc32 = sctp_start_cksum(skb->data + offset,
- skb_headlen(skb) - offset);
- skb_walk_frags(skb, iter)
- crc32 = sctp_update_cksum((__u8 *) iter->data,
- skb_headlen(iter), crc32);
+ sh->checksum = 0;
+ ret = cpu_to_le32(~__skb_checksum(skb, offset, skb->len - offset,
+ ~(__u32)0, &ops));
+ sh->checksum = old;
- return sctp_end_cksum(crc32);
+ return ret;
}
#endif /* __sctp_checksum_h__ */