[PATCH net v5] xen-netback: fix fragment detection in checksum setup
From: Paul Durrant <hidden>
Date: 2013-12-03 17:39:33
The code to detect fragments in checksum_setup() was missing for IPv4 and too eager for IPv6. (It transpires that Windows seems to send IPv6 packets with a fragment header even if they are not a fragment - i.e. offset is zero, and M bit is not set). This patch also incorporates a fix to callers of maybe_pull_tail() where skb->network_header was being erroneously added to the length argument. Signed-off-by: Paul Durrant <redacted> Signed-off-by: Zoltan Kiss <redacted> Cc: Wei Liu <redacted> Cc: Ian Campbell <redacted> Cc: David Vrabel <redacted> cc: David Miller <davem@davemloft.net> --- v5 - Return an error from maybe_pull_tail() to distiguish issues due to the frontend from those due to the backend. v4 - Re-work maybe_pull_tail() to have a failure path and update mac and network header pointers on success. - Re-work callers of maybe_pull_tail() to handle failures and allow for movement of skb header pointers. - Incorporate fixes from patch "Fix pull size in checksum_setup_ip" since it also modifies callers of maybe_pull_tail(). - Remove error messages in checksum routines that could be triggered by frontends v3 - Use defined values for 'fragment offset' and 'more fragments' v2 - Added comments noting what fragment/offset masks mean drivers/net/xen-netback/netback.c | 236 +++++++++++++++++++++---------------- include/linux/ipv6.h | 1 + include/net/ipv6.h | 3 +- 3 files changed, 140 insertions(+), 100 deletions(-)
diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index 64f0e0d..acf1392 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c@@ -1149,49 +1149,72 @@ static int xenvif_set_skb_gso(struct xenvif *vif, return 0; } -static inline void maybe_pull_tail(struct sk_buff *skb, unsigned int len) +static inline int maybe_pull_tail(struct sk_buff *skb, unsigned int len, + unsigned int max) { - if (skb_is_nonlinear(skb) && skb_headlen(skb) < len) { - /* If we need to pullup then pullup to the max, so we - * won't need to do it again. - */ - int target = min_t(int, skb->len, MAX_TCP_HEADER); - __pskb_pull_tail(skb, target - skb_headlen(skb)); - } + if (skb_headlen(skb) >= len) + return 0; + + /* If we need to pullup then pullup to the max, so we + * won't need to do it again. + */ + if (max > skb->len) + max = skb->len; + + if (__pskb_pull_tail(skb, max - skb_headlen(skb)) == NULL) + return -ENOMEM; + + if (skb_headlen(skb) < len) + return -EPROTO; + + return 0; } +/* This value should be large enough to cover a tagged ethernet header plus + * maximally sized IP and TCP or UDP headers. + */ +#define MAX_IP_HDR_LEN 128 + static int checksum_setup_ip(struct xenvif *vif, struct sk_buff *skb, int recalculate_partial_csum) { - struct iphdr *iph = (void *)skb->data; - unsigned int header_size; unsigned int off; - int err = -EPROTO; + bool fragment; + int err; + + fragment = false; + + err = maybe_pull_tail(skb, + sizeof(struct iphdr), + MAX_IP_HDR_LEN); + if (err < 0) + goto out; - off = sizeof(struct iphdr); + if (ip_hdr(skb)->frag_off & htons(IP_OFFSET | IP_MF)) + fragment = true; - header_size = skb->network_header + off + MAX_IPOPTLEN; - maybe_pull_tail(skb, header_size); + off = ip_hdrlen(skb); - off = iph->ihl * 4; + err = -EPROTO; - switch (iph->protocol) { + switch (ip_hdr(skb)->protocol) { case IPPROTO_TCP: if (!skb_partial_csum_set(skb, off, offsetof(struct tcphdr, check))) goto out; if (recalculate_partial_csum) { - struct tcphdr *tcph = tcp_hdr(skb); - - header_size = skb->network_header + - off + - sizeof(struct tcphdr); - maybe_pull_tail(skb, header_size); - - tcph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, - skb->len - off, - IPPROTO_TCP, 0); + err = maybe_pull_tail(skb, + off + sizeof(struct tcphdr), + MAX_IP_HDR_LEN); + if (err < 0) + goto out; + + tcp_hdr(skb)->check = + ~csum_tcpudp_magic(ip_hdr(skb)->saddr, + ip_hdr(skb)->daddr, + skb->len - off, + IPPROTO_TCP, 0); } break; case IPPROTO_UDP:
@@ -1200,24 +1223,20 @@ static int checksum_setup_ip(struct xenvif *vif, struct sk_buff *skb, goto out; if (recalculate_partial_csum) { - struct udphdr *udph = udp_hdr(skb); - - header_size = skb->network_header + - off + - sizeof(struct udphdr); - maybe_pull_tail(skb, header_size); - - udph->check = ~csum_tcpudp_magic(iph->saddr, iph->daddr, - skb->len - off, - IPPROTO_UDP, 0); + err = maybe_pull_tail(skb, + off + sizeof(struct udphdr), + MAX_IP_HDR_LEN); + if (err < 0) + goto out; + + udp_hdr(skb)->check = + ~csum_tcpudp_magic(ip_hdr(skb)->saddr, + ip_hdr(skb)->daddr, + skb->len - off, + IPPROTO_UDP, 0); } break; default: - if (net_ratelimit()) - netdev_err(vif->dev, - "Attempting to checksum a non-TCP/UDP packet, " - "dropping a protocol %d packet\n", - iph->protocol); goto out; }
@@ -1227,75 +1246,99 @@ out: return err; } +/* This value should be large enough to cover a tagged ethernet header plus + * an IPv6 header, all options, and a maximal TCP or UDP header. + */ +#define MAX_IPV6_HDR_LEN 256 + +#define OPT_HDR(type, skb, off) \ + (type *)(skb_network_header(skb) + (off)) + static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb, int recalculate_partial_csum) { - int err = -EPROTO; - struct ipv6hdr *ipv6h = (void *)skb->data; + int err; u8 nexthdr; - unsigned int header_size; unsigned int off; + unsigned int len; bool fragment; bool done; + fragment = false; done = false; off = sizeof(struct ipv6hdr); - header_size = skb->network_header + off; - maybe_pull_tail(skb, header_size); + err = maybe_pull_tail(skb, off, MAX_IPV6_HDR_LEN); + if (err < 0) + goto out; - nexthdr = ipv6h->nexthdr; + nexthdr = ipv6_hdr(skb)->nexthdr; - while ((off <= sizeof(struct ipv6hdr) + ntohs(ipv6h->payload_len)) && - !done) { + len = sizeof(struct ipv6hdr) + ntohs(ipv6_hdr(skb)->payload_len); + while (off <= len && !done) { switch (nexthdr) { case IPPROTO_DSTOPTS: case IPPROTO_HOPOPTS: case IPPROTO_ROUTING: { - struct ipv6_opt_hdr *hp = (void *)(skb->data + off); + struct ipv6_opt_hdr *hp; - header_size = skb->network_header + - off + - sizeof(struct ipv6_opt_hdr); - maybe_pull_tail(skb, header_size); + err = maybe_pull_tail(skb, + off + + sizeof(struct ipv6_opt_hdr), + MAX_IPV6_HDR_LEN); + if (err < 0) + goto out; + hp = OPT_HDR(struct ipv6_opt_hdr, skb, off); nexthdr = hp->nexthdr; off += ipv6_optlen(hp); break; } case IPPROTO_AH: { - struct ip_auth_hdr *hp = (void *)(skb->data + off); + struct ip_auth_hdr *hp; + + err = maybe_pull_tail(skb, + off + + sizeof(struct ip_auth_hdr), + MAX_IPV6_HDR_LEN); + if (err < 0) + goto out; + + hp = OPT_HDR(struct ip_auth_hdr, skb, off); + nexthdr = hp->nexthdr; + off += ipv6_authlen(hp); + break; + } + case IPPROTO_FRAGMENT: { + struct frag_hdr *hp; - header_size = skb->network_header + - off + - sizeof(struct ip_auth_hdr); - maybe_pull_tail(skb, header_size); + err = maybe_pull_tail(skb, + off + + sizeof(struct frag_hdr), + MAX_IPV6_HDR_LEN); + if (err < 0) + goto out; + + hp = OPT_HDR(struct frag_hdr, skb, off); + + if (hp->frag_off & htons(IP6_OFFSET | IP6_MF)) + fragment = true; nexthdr = hp->nexthdr; - off += (hp->hdrlen+2)<<2; + off += sizeof(struct frag_hdr); break; } - case IPPROTO_FRAGMENT: - fragment = true; - /* fall through */ default: done = true; break; } } - if (!done) { - if (net_ratelimit()) - netdev_err(vif->dev, "Failed to parse packet header\n"); - goto out; - } + err = -EPROTO; - if (fragment) { - if (net_ratelimit()) - netdev_err(vif->dev, "Packet is a fragment!\n"); + if (!done || fragment) goto out; - } switch (nexthdr) { case IPPROTO_TCP:
@@ -1304,17 +1347,17 @@ static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb, goto out; if (recalculate_partial_csum) { - struct tcphdr *tcph = tcp_hdr(skb); - - header_size = skb->network_header + - off + - sizeof(struct tcphdr); - maybe_pull_tail(skb, header_size); - - tcph->check = ~csum_ipv6_magic(&ipv6h->saddr, - &ipv6h->daddr, - skb->len - off, - IPPROTO_TCP, 0); + err = maybe_pull_tail(skb, + off + sizeof(struct tcphdr), + MAX_IPV6_HDR_LEN); + if (err < 0) + goto out; + + tcp_hdr(skb)->check = + ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr, + &ipv6_hdr(skb)->daddr, + skb->len - off, + IPPROTO_TCP, 0); } break; case IPPROTO_UDP:
@@ -1323,25 +1366,20 @@ static int checksum_setup_ipv6(struct xenvif *vif, struct sk_buff *skb, goto out; if (recalculate_partial_csum) { - struct udphdr *udph = udp_hdr(skb); - - header_size = skb->network_header + - off + - sizeof(struct udphdr); - maybe_pull_tail(skb, header_size); - - udph->check = ~csum_ipv6_magic(&ipv6h->saddr, - &ipv6h->daddr, - skb->len - off, - IPPROTO_UDP, 0); + err = maybe_pull_tail(skb, + off + sizeof(struct udphdr), + MAX_IPV6_HDR_LEN); + if (err < 0) + goto out; + + udp_hdr(skb)->check = + ~csum_ipv6_magic(&ipv6_hdr(skb)->saddr, + &ipv6_hdr(skb)->daddr, + skb->len - off, + IPPROTO_UDP, 0); } break; default: - if (net_ratelimit()) - netdev_err(vif->dev, - "Attempting to checksum a non-TCP/UDP packet, " - "dropping a protocol %d packet\n", - nexthdr); goto out; }
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 5d89d1b..c56c350 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h@@ -4,6 +4,7 @@ #include <uapi/linux/ipv6.h> #define ipv6_optlen(p) (((p)->hdrlen+1) << 3) +#define ipv6_authlen(p) (((p)->hdrlen+2) << 2) /* * This structure contains configuration options per IPv6 link. */
diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index eb198ac..488316e 100644
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h@@ -110,7 +110,8 @@ struct frag_hdr { __be32 identification; }; -#define IP6_MF 0x0001 +#define IP6_MF 0x0001 +#define IP6_OFFSET 0xFFF8 #include <net/sock.h>
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1.7.10.4