From: Ben Pfaff Date: Mon, 4 Aug 2008 21:18:24 +0000 (-0700) Subject: Don't accept incomplete TCP headers when extracting flows in kernel. X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ef7e8993ff134f9dbfa72e86cc91cb149deca7bf;p=openvswitch Don't accept incomplete TCP headers when extracting flows in kernel. This makes the kernel and the userspace implementations of flow extraction behave the same way regarding headers. --- diff --git a/datapath/flow.c b/datapath/flow.c index d4c48021..c49a4cb1 100644 --- a/datapath/flow.c +++ b/datapath/flow.c @@ -193,13 +193,29 @@ void print_flow(const struct sw_flow_key *key) } EXPORT_SYMBOL(print_flow); +static int tcphdr_ok(struct sk_buff *skb) +{ + int th_ofs = skb_transport_offset(skb); + if (skb->len >= th_ofs + sizeof(struct tcphdr)) { + int tcp_len = tcp_hdrlen(skb); + return (tcp_len >= sizeof(struct tcphdr) + && skb->len >= th_ofs + tcp_len); + } + return 0; +} + +static int udphdr_ok(struct sk_buff *skb) +{ + int th_ofs = skb_transport_offset(skb); + return skb->len >= th_ofs + sizeof(struct udphdr); +} + /* Parses the Ethernet frame in 'skb', which was received on 'in_port', * and initializes 'key' to match. */ void flow_extract(struct sk_buff *skb, uint16_t in_port, struct sw_flow_key *key) { struct ethhdr *mac; - struct udphdr *th; int nh_ofs, th_ofs; key->in_port = htons(in_port); @@ -251,20 +267,41 @@ void flow_extract(struct sk_buff *skb, uint16_t in_port, skb_set_transport_header(skb, th_ofs); /* Transport layer. */ - if ((key->nw_proto != IPPROTO_TCP && key->nw_proto != IPPROTO_UDP) - || skb->len < th_ofs + sizeof(struct udphdr) - || nh->frag_off & htons(IP_MF | IP_OFFSET)) { + if (!(nh->frag_off & htons(IP_MF | IP_OFFSET))) { + if (key->nw_proto == IPPROTO_TCP) { + if (tcphdr_ok(skb)) { + struct tcphdr *tcp = tcp_hdr(skb); + key->tp_src = tcp->source; + key->tp_dst = tcp->dest; + } else { + /* Avoid tricking other code into + * thinking that this packet has an L4 + * header. */ + goto no_proto; + } + } else if (key->nw_proto == IPPROTO_UDP) { + if (udphdr_ok(skb)) { + struct udphdr *udp = udp_hdr(skb); + key->tp_src = udp->source; + key->tp_dst = udp->dest; + } else { + /* Avoid tricking other code into + * thinking that this packet has an L4 + * header. */ + goto no_proto; + } + } + } else { goto no_th; } - th = udp_hdr(skb); - key->tp_src = th->source; - key->tp_dst = th->dest; return; } key->nw_src = 0; key->nw_dst = 0; + +no_proto: key->nw_proto = 0; no_th: