Commit f36c23bb authored by Gerrit Renker's avatar Gerrit Renker Committed by David S. Miller
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udplite: fast-path computation of checksum coverage 



Commit 903ab86d of 1 March this year ("udp: Add
lockless transmit path") introduced a new fast TX path that broke the checksum
coverage computation of UDP-lite, which so far depended on up->len (only set
if the socket is locked and 0 in the fast path).

Fixed by providing both fast- and slow-path computation of checksum coverage.
The latter can be removed when UDP(-lite)v6 also uses a lockless transmit path.
 
Reported-by: default avatarThomas Volkert <thomas@homer-conferencing.com>
Signed-off-by: default avatarGerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 4c41042d

include/net/udplite.h

+31 −32
Original line number Diff line number Diff line
@@ -66,21 +66,22 @@ static inline int udplite_checksum_init(struct sk_buff *skb, struct udphdr *uh) 
	return 0;

}



static inline int udplite_sender_cscov(struct udp_sock *up, struct udphdr *uh)

/* Slow-path computation of checksum. Socket is locked. */

static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)

{

	const struct udp_sock *up = udp_sk(skb->sk);

	int cscov = up->len;

	__wsum csum = 0;



	if (up->pcflag & UDPLITE_SEND_CC) {

		/*

	 * Sender has set `partial coverage' option on UDP-Lite socket

		 * Sender has set `partial coverage' option on UDP-Lite socket.

		 * The special case "up->pcslen == 0" signifies full coverage.

		 */

	if (up->pcflag & UDPLITE_SEND_CC)    {

		if (up->pcslen < up->len) {

		/* up->pcslen == 0 means that full coverage is required,

		 * partial coverage only if  0 < up->pcslen < up->len */

			if (0 < up->pcslen) {

			if (0 < up->pcslen)

				cscov = up->pcslen;

			}

			uh->len = htons(up->pcslen);

			udp_hdr(skb)->len = htons(up->pcslen);

		}

		/*

		 * NOTE: Causes for the error case  `up->pcslen > up->len':
@@ -93,13 +94,6 @@ static inline int udplite_sender_cscov(struct udp_sock *up, struct udphdr *uh) 
		 *       illegal, we fall back to the defaults here.

		 */

	}

	return cscov;

}



static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb)

{

	int cscov = udplite_sender_cscov(udp_sk(sk), udp_hdr(skb));

	__wsum csum = 0;



	skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */
@@ -115,16 +109,21 @@ static inline __wsum udplite_csum_outgoing(struct sock *sk, struct sk_buff *skb) 
	return csum;

}



/* Fast-path computation of checksum. Socket may not be locked. */

static inline __wsum udplite_csum(struct sk_buff *skb)

{

	struct sock *sk = skb->sk;

	int cscov = udplite_sender_cscov(udp_sk(sk), udp_hdr(skb));

	const struct udp_sock *up = udp_sk(skb->sk);

	const int off = skb_transport_offset(skb);

	const int len = skb->len - off;

	int len = skb->len - off;



	if ((up->pcflag & UDPLITE_SEND_CC) && up->pcslen < len) {

		if (0 < up->pcslen)

			len = up->pcslen;

		udp_hdr(skb)->len = htons(up->pcslen);

	}

	skb->ip_summed = CHECKSUM_NONE;     /* no HW support for checksumming */



	return skb_checksum(skb, off, min(cscov, len), 0);

	return skb_checksum(skb, off, len, 0);

}



extern void	udplite4_register(void);

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