On Sun, Sep 28, 2025 at 10:45:12AM +0200, Sven Eckelmann wrote:
> On Saturday, 27 September 2025 22:55:52 CEST Eric Biggers wrote:
> > Hi,
> >
> > On Tue, Sep 16, 2025 at 02:24:40PM +0200, Simon Wunderlich wrote:
> > > +static __be32 batadv_skb_crc32(struct sk_buff *skb, u8 *payload_ptr)
> > > +{
> > > + unsigned int to = skb->len;
> > > + unsigned int consumed = 0;
> > > + struct skb_seq_state st;
> > > + unsigned int from;
> > > + unsigned int len;
> > > + const u8 *data;
> > > + u32 crc = 0;
> > > +
> > > + from = (unsigned int)(payload_ptr - skb->data);
> > > +
> > > + skb_prepare_seq_read(skb, from, to, &st);
> > > + while ((len = skb_seq_read(consumed, &data, &st)) != 0) {
> > > + crc = crc32c(crc, data, len);
> > > + consumed += len;
> > > + }
> > > +
> > > + return htonl(crc);
> > > +}
> >
> > Has using skb_crc32c() been considered here?
>
> No. At the time this was written (v3.8), skb_crc32c (v6.16) didnt exist. Also
> its predecessor __skb_checksum only started its existence in v3.13. And no
> one
> noticed it as candidate to replace batadv_skb_crc32 with
>
> And this patch here was just moving the function between two places - so not
> introducing new code.
>
> Do you want to submit a patch to integrate your new function in batman-adv? I
> only performed a quick-and-dirty test to see if it returns the same results
> and it seemed to do its job fine.
>
> diff --git c/net/batman-adv/Kconfig w/net/batman-adv/Kconfig
> index c299e2bc..58c408b7 100644
> --- c/net/batman-adv/Kconfig
> +++ w/net/batman-adv/Kconfig
> @@ -35,6 +35,7 @@ config BATMAN_ADV_BLA
> bool "Bridge Loop Avoidance"
> depends on BATMAN_ADV && INET
> select CRC16
> + select NET_CRC32C
> default y
> help
> This option enables BLA (Bridge Loop Avoidance), a mechanism
> diff --git c/net/batman-adv/bridge_loop_avoidance.c
> w/net/batman-adv/bridge_loop_avoidance.c
> index b992ba12..eef40b6f 100644
> --- c/net/batman-adv/bridge_loop_avoidance.c
> +++ w/net/batman-adv/bridge_loop_avoidance.c
> @@ -12,7 +12,6 @@
> #include <linux/compiler.h>
> #include <linux/container_of.h>
> #include <linux/crc16.h>
> -#include <linux/crc32.h>
> #include <linux/err.h>
> #include <linux/errno.h>
> #include <linux/etherdevice.h>
> @@ -1585,45 +1584,11 @@ int batadv_bla_init(struct batadv_priv *bat_priv)
> return 0;
> }
>
> -/**
> - * batadv_skb_crc32() - calculate CRC32 of the whole packet and skip bytes in
> - * the header
> - * @skb: skb pointing to fragmented socket buffers
> - * @payload_ptr: Pointer to position inside the head buffer of the skb
> - * marking the start of the data to be CRC'ed
> - *
> - * payload_ptr must always point to an address in the skb head buffer and
> not to
> - * a fragment.
> - *
> - * Return: big endian crc32c of the checksummed data
> - */
> -static __be32 batadv_skb_crc32(struct sk_buff *skb, u8 *payload_ptr)
> -{
> - unsigned int to = skb->len;
> - unsigned int consumed = 0;
> - struct skb_seq_state st;
> - unsigned int from;
> - unsigned int len;
> - const u8 *data;
> - u32 crc = 0;
> -
> - from = (unsigned int)(payload_ptr - skb->data);
> -
> - skb_prepare_seq_read(skb, from, to, &st);
> - while ((len = skb_seq_read(consumed, &data, &st)) != 0) {
> - crc = crc32c(crc, data, len);
> - consumed += len;
> - }
> -
> - return htonl(crc);
> -}
> -
> /**
> * batadv_bla_check_duplist() - Check if a frame is in the broadcast dup.
> * @bat_priv: the bat priv with all the mesh interface information
> * @skb: contains the multicast packet to be checked
> - * @payload_ptr: pointer to position inside the head buffer of the skb
> - * marking the start of the data to be CRC'ed
> + * @payload_offset: offset in the skb, marking the start of the data to be
> CRC'ed
> * @orig: originator mac address, NULL if unknown
> *
> * Check if it is on our broadcast list. Another gateway might have sent the
> @@ -1638,16 +1603,18 @@ static __be32 batadv_skb_crc32(struct sk_buff *skb,
> u8 *payload_ptr)
> * Return: true if a packet is in the duplicate list, false otherwise.
> */
> static bool batadv_bla_check_duplist(struct batadv_priv *bat_priv,
> - struct sk_buff *skb, u8 *payload_ptr,
> + struct sk_buff *skb, int payload_offset,
> const u8 *orig)
> {
> struct batadv_bcast_duplist_entry *entry;
> bool ret = false;
> + int payload_len;
> int i, curr;
> __be32 crc;
>
> /* calculate the crc ... */
> - crc = batadv_skb_crc32(skb, payload_ptr);
> + payload_len = skb->len - payload_offset;
> + crc = htonl(skb_crc32c(skb, payload_offset, payload_len, 0));
>
> spin_lock_bh(&bat_priv->bla.bcast_duplist_lock);
>
> @@ -1727,7 +1694,7 @@ static bool batadv_bla_check_duplist(struct batadv_priv
> *bat_priv,
> static bool batadv_bla_check_ucast_duplist(struct batadv_priv *bat_priv,
> struct sk_buff *skb)
> {
> - return batadv_bla_check_duplist(bat_priv, skb, (u8 *)skb->data, NULL);
> + return batadv_bla_check_duplist(bat_priv, skb, 0, NULL);
> }
>
> /**
> @@ -1745,12 +1712,10 @@ bool batadv_bla_check_bcast_duplist(struct
> batadv_priv *bat_priv,
> struct sk_buff *skb)
> {
> struct batadv_bcast_packet *bcast_packet;
> - u8 *payload_ptr;
>
> bcast_packet = (struct batadv_bcast_packet *)skb->data;
> - payload_ptr = (u8 *)(bcast_packet + 1);
>
> - return batadv_bla_check_duplist(bat_priv, skb, payload_ptr,
> + return batadv_bla_check_duplist(bat_priv, skb, sizeof(*bcast_packet),
> bcast_packet->orig);
> }
It looks like you're already most of the way there, so I suggest you
send the patch. Thanks!
- Eric
