skb_partial_csum_set (9)

bool skb_partial_csum_set(struct sk_buff * skb, u16 start, u16 off);

skb

the skb to set

start

the number of bytes after skb->data to start checksumming.

off

the offset from start to place the checksum.

For untrusted partially-checksummed packets, we need to make sure the values for skb->csum_start and skb->csum_offset are valid so we don't oops.

This function checks and sets those values and skb->ip_summed: if this returns false you should drop the packet.