From: Linas Vepstas Date: Tue, 17 Apr 2007 05:54:13 +0000 (-0700) Subject: spidernet: Fix problem sending IP fragments X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=33bdeec80649f2eab36039f63d69c65378493cbe;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git spidernet: Fix problem sending IP fragments The basic structure of "normal" UDP/IP/Ethernet frames (that actually work): - It starts with the Ethernet header (dest MAC, src MAC, etc.) - The next part is occupied by the IP header (version info, length of packet, id=0, fragment offset=0, checksum, from / to address, etc.) - Then comes the UDP header (src / dest port, length, checksum) - Actual payload - Ethernet checksum Now what's different for IP fragment: - The IP header has id set to some value (same for all fragments), offset is set appropriately (i.e. 0 for first fragment, following according to size of other fragments), size is the length of the frame. - UDP header is unchanged. I.e. length is according to full UDP datagram, not just the part within the actual frame! But this is only true within the first frame: all following frames don't have a valid UDP-header at all. The spidernet silicon seems to be quite intelligent: It's able to compute (IP / UDP / Ethernet) checksums on the fly and tests if frames are conforming to RFC -- at least conforming to RFC on complete frames. But IP fragments are different as explained above: I.e. for IP fragments containing part of a UDP datagram it sees incompatible length in the headers for IP and UDP in the first frame and, thus, skips this frame. But the content *is* correct for IP fragments. For all following frames it finds (most probably) no valid UDP header at all. But this *is* also correct for IP fragments. The Linux IP-stack seems to be clever in this point. It expects the spidernet to calculate the checksum (since the module claims to be able to do so) and marks the skb's for "normal" frames accordingly (ip_summed set to CHECKSUM_HW). But for the IP fragments it does not expect the driver to be capable to handle the frames appropriately. Thus all checksums are allready computed. This is also flaged within the skb (ip_summed set to CHECKSUM_NONE). Unfortunately the spidernet driver ignores that hints. It tries to send the IP fragments of UDP datagrams as normal UDP/IP frames. Since they have different structure the silicon detects them the be not "well-formed" and skips them. The following one-liner against 2.6.21-rc2 changes this behavior. If the IP-stack claims to have done the checksumming, the driver should not try to checksum (and analyze) the frame but send it as is. Signed-off-by: Norbert Eicker Signed-off-by: Linas Vepstas Signed-off-by: Andrew Morton Signed-off-by: Jeff Garzik --- diff --git a/drivers/net/spider_net.c b/drivers/net/spider_net.c index 3b91af89e4c7..e3019d52c30f 100644 --- a/drivers/net/spider_net.c +++ b/drivers/net/spider_net.c @@ -719,7 +719,7 @@ spider_net_prepare_tx_descr(struct spider_net_card *card, SPIDER_NET_DESCR_CARDOWNED | SPIDER_NET_DMAC_NOCS; spin_unlock_irqrestore(&chain->lock, flags); - if (skb->protocol == htons(ETH_P_IP)) + if (skb->protocol == htons(ETH_P_IP) && skb->ip_summed == CHECKSUM_PARTIAL) switch (skb->nh.iph->protocol) { case IPPROTO_TCP: hwdescr->dmac_cmd_status |= SPIDER_NET_DMAC_TCP;