net [BUG-FIX][PATCH 1/1] udplite: fast-path computation of checksum coverage
From: Gerrit Renker <hidden>
Date: 2011-10-17 21:35:03
Hi Dave, can you please consider the fix below -- the checksum coverage in UDP-Lite had been broken for over half a year; then reported by Thomas. I have tested the patch below in various scenarios with IPv4 and IPv6, on localhost, and between multiple hosts. Gerrit
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
quoted
Patch <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
udplite: fast-path computation of checksum coverage
Commit 903ab86d195cca295379699299c5fc10beba31c7 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: Thomas Volkert <redacted>
Signed-off-by: Gerrit Renker <redacted>
---
include/net/udplite.h | 63 ++++++++++++++++++++++++--------------------------
1 file changed, 31 insertions(+), 32 deletions(-)
--- a/include/net/udplite.h
+++ b/include/net/udplite.h@@ -66,40 +66,34 @@ 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; - /* - * Sender has set `partial coverage' option on UDP-Lite socket - */ - if (up->pcflag & UDPLITE_SEND_CC) { + if (up->pcflag & UDPLITE_SEND_CC) { + /* + * Sender has set `partial coverage' option on UDP-Lite socket. + * The special case "up->pcslen == 0" signifies full coverage. + */ 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) { - cscov = up->pcslen; - } - uh->len = htons(up->pcslen); + if (0 < up->pcslen) + cscov = up->pcslen; + udp_hdr(skb)->len = htons(up->pcslen); } - /* - * NOTE: Causes for the error case `up->pcslen > up->len': - * (i) Application error (will not be penalized). - * (ii) Payload too big for send buffer: data is split - * into several packets, each with its own header. - * In this case (e.g. last segment), coverage may - * exceed packet length. - * Since packets with coverage length > packet length are - * illegal, we fall back to the defaults here. - */ + /* + * NOTE: Causes for the error case `up->pcslen > up->len': + * (i) Application error (will not be penalized). + * (ii) Payload too big for send buffer: data is split + * into several packets, each with its own header. + * In this case (e.g. last segment), coverage may + * exceed packet length. + * Since packets with coverage length > packet length are + * 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);