skb_sctp_csum_help is like skb_checksum_help, but it is designed for checksumming SCTP packets using crc32c (see RFC3309), provided that sctp.ko has been loaded before. In case sctp.ko is not loaded, invoking skb_sctp_csum_help on a skb results in the following printout: sk_buff: attempt to compute crc32c without sctp.ko Signed-off-by: Davide Caratti <dcaratti@xxxxxxxxxx> --- include/linux/netdevice.h | 1 + include/linux/skbuff.h | 3 ++- net/core/dev.c | 40 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 43 insertions(+), 1 deletion(-) diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index f40f0ab..8c34735 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -3918,6 +3918,7 @@ void netdev_rss_key_fill(void *buffer, size_t len); int dev_get_nest_level(struct net_device *dev); int skb_checksum_help(struct sk_buff *skb); +int skb_sctp_csum_help(struct sk_buff *skb); struct sk_buff *__skb_gso_segment(struct sk_buff *skb, netdev_features_t features, bool tx_path); struct sk_buff *skb_mac_gso_segment(struct sk_buff *skb, diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index cab9a32..0671131 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -192,7 +192,8 @@ * accordingly. Note the there is no indication in the skbuff that the * CHECKSUM_PARTIAL refers to an SCTP checksum, a driver that supports * both IP checksum offload and SCTP CRC offload must verify which offload - * is configured for a packet presumably by inspecting packet headers. + * is configured for a packet presumably by inspecting packet headers; in + * case, skb_sctp_csum_help is provided to compute CRC on SCTP packets. * * NETIF_F_FCOE_CRC - This feature indicates that a device is capable of * offloading the FCOE CRC in a packet. To perform this offload the stack diff --git a/net/core/dev.c b/net/core/dev.c index 05d19c6..b9fb843 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -140,6 +140,7 @@ #include <linux/hrtimer.h> #include <linux/netfilter_ingress.h> #include <linux/crash_dump.h> +#include <linux/sctp.h> #include "net-sysfs.h" @@ -2578,6 +2579,45 @@ int skb_checksum_help(struct sk_buff *skb) } EXPORT_SYMBOL(skb_checksum_help); +int skb_sctp_csum_help(struct sk_buff *skb) +{ + __le32 crc32c_csum; + int ret = 0, offset; + + if (skb->ip_summed != CHECKSUM_PARTIAL) + goto out; + + if (unlikely(skb_is_gso(skb))) + goto out; + + /* Before computing a checksum, we should make sure no frag could + * be modified by an external entity : checksum could be wrong. + */ + if (unlikely(skb_has_shared_frag(skb))) { + ret = __skb_linearize(skb); + if (ret) + goto out; + } + + offset = skb_checksum_start_offset(skb); + crc32c_csum = cpu_to_le32(~__skb_checksum(skb, offset, + skb->len - offset, ~(__u32)0, + sctp_csum_stub)); + offset += offsetof(struct sctphdr, checksum); + BUG_ON(offset >= skb_headlen(skb)); + + if (skb_cloned(skb) && + !skb_clone_writable(skb, offset + sizeof(__le32))) { + ret = pskb_expand_head(skb, 0, 0, GFP_ATOMIC); + if (ret) + goto out; + } + *(__le32 *)(skb->data + offset) = crc32c_csum; + skb->ip_summed = CHECKSUM_NONE; +out: + return ret; +} + __be16 skb_network_protocol(struct sk_buff *skb, int *depth) { __be16 type = skb->protocol; -- 2.7.4 -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html