From: Al Viro Date: Fri, 3 Nov 2006 08:28:23 +0000 (-0800) Subject: [IPX]: Annotate and fix IPX checksum X-Git-Tag: v2.6.19-rc5~19^2~10 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=02e60370d4dac83f22d5ae75d5512bcb9a3f24b7;p=linux-2.6 [IPX]: Annotate and fix IPX checksum Calculation of IPX checksum got buggered about 2.4.0. The old variant mangled the packet; that got fixed, but calculation itself got buggered. Restored the correct logics, fixed a subtle breakage we used to have even back then: if the sum is 0 mod 0xffff, we want to return 0, not 0xffff. The latter has special meaning for IPX (cheksum disabled). Observation (and obvious fix) nicked from history of FreeBSD ipx_cksum.c... Signed-off-by: Al Viro Signed-off-by: David S. Miller --- diff --git a/include/net/ipx.h b/include/net/ipx.h index 4a423d2695..c6b2ee6108 100644 --- a/include/net/ipx.h +++ b/include/net/ipx.h @@ -26,8 +26,8 @@ struct ipx_address { #define IPX_MAX_PPROP_HOPS 8 struct ipxhdr { - __u16 ipx_checksum __attribute__ ((packed)); -#define IPX_NO_CHECKSUM 0xFFFF + __be16 ipx_checksum __attribute__ ((packed)); +#define IPX_NO_CHECKSUM __constant_htons(0xFFFF) __be16 ipx_pktsize __attribute__ ((packed)); __u8 ipx_tctrl; __u8 ipx_type; diff --git a/net/ipx/af_ipx.c b/net/ipx/af_ipx.c index c272a38af3..76c661566d 100644 --- a/net/ipx/af_ipx.c +++ b/net/ipx/af_ipx.c @@ -1234,27 +1234,27 @@ static int ipxitf_ioctl(unsigned int cmd, void __user *arg) /* Note: We assume ipx_tctrl==0 and htons(length)==ipx_pktsize */ /* This functions should *not* mess with packet contents */ -__u16 ipx_cksum(struct ipxhdr *packet, int length) +__be16 ipx_cksum(struct ipxhdr *packet, int length) { /* * NOTE: sum is a net byte order quantity, which optimizes the * loop. This only works on big and little endian machines. (I * don't know of a machine that isn't.) */ - /* start at ipx_dest - We skip the checksum field and start with - * ipx_type before the loop, not considering ipx_tctrl in the calc */ - __u16 *p = (__u16 *)&packet->ipx_dest; - __u32 i = (length >> 1) - 1; /* Number of complete words */ - __u32 sum = packet->ipx_type << sizeof(packet->ipx_tctrl); - - /* Loop through all complete words except the checksum field, - * ipx_type (accounted above) and ipx_tctrl (not used in the cksum) */ - while (--i) + /* handle the first 3 words separately; checksum should be skipped + * and ipx_tctrl masked out */ + __u16 *p = (__u16 *)packet; + __u32 sum = p[1] + (p[2] & (__force u16)htons(0x00ff)); + __u32 i = (length >> 1) - 3; /* Number of remaining complete words */ + + /* Loop through them */ + p += 3; + while (i--) sum += *p++; /* Add on the last part word if it exists */ if (packet->ipx_pktsize & htons(1)) - sum += ntohs(0xff00) & *p; + sum += (__force u16)htons(0xff00) & *p; /* Do final fixup */ sum = (sum & 0xffff) + (sum >> 16); @@ -1263,7 +1263,14 @@ __u16 ipx_cksum(struct ipxhdr *packet, int length) if (sum >= 0x10000) sum++; - return ~sum; + /* + * Leave 0 alone; we don't want 0xffff here. Note that we can't get + * here with 0x10000, so this check is the same as ((__u16)sum) + */ + if (sum) + sum = ~sum; + + return (__force __be16)sum; } const char *ipx_frame_name(__be16 frame) diff --git a/net/ipx/ipx_route.c b/net/ipx/ipx_route.c index 8bfaefaf88..68560ee0d7 100644 --- a/net/ipx/ipx_route.c +++ b/net/ipx/ipx_route.c @@ -19,7 +19,7 @@ DEFINE_RWLOCK(ipx_routes_lock); extern struct ipx_interface *ipx_internal_net; -extern __u16 ipx_cksum(struct ipxhdr *packet, int length); +extern __be16 ipx_cksum(struct ipxhdr *packet, int length); extern struct ipx_interface *ipxitf_find_using_net(__be32 net); extern int ipxitf_demux_socket(struct ipx_interface *intrfc, struct sk_buff *skb, int copy); @@ -238,7 +238,7 @@ int ipxrtr_route_packet(struct sock *sk, struct sockaddr_ipx *usipx, /* Apply checksum. Not allowed on 802.3 links. */ if (sk->sk_no_check || intrfc->if_dlink_type == htons(IPX_FRAME_8023)) - ipx->ipx_checksum = 0xFFFF; + ipx->ipx_checksum = htons(0xFFFF); else ipx->ipx_checksum = ipx_cksum(ipx, len + sizeof(struct ipxhdr));