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forecast: Only reinject packets that are marked or from the configured interface

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This seems to avoid broadcast loops (i.e. processing and reinjecting the
same broadcast packet over and over again) as the packets we send via
AF_PACKET socket are neither marked nor from that interface.
This commit is contained in:
Tobias Brunner 2019-02-05 17:21:21 +01:00
parent 00a953d090
commit 83674787d5
1 changed files with 8 additions and 2 deletions
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10
src/libcharon/plugins/forecast/forecast_forwarder.c
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@ -317,9 +317,15 @@ static void join_groups(private_kernel_listener_t *this, struct sockaddr *addr)
/**
* Attach the socket filter to the socket
*/
static bool attach_filter(int fd, uint32_t broadcast)
static bool attach_filter(int fd, uint32_t broadcast, uint32_t ifindex)
{
struct sock_filter filter_code[] = {
/* handle any marked packets (from clients) */
BPF_STMT(BPF_LD+BPF_B+BPF_ABS, SKF_AD_OFF+SKF_AD_MARK),
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, 0, 0, 2),
/* and those from the internal interface */
BPF_STMT(BPF_LD+BPF_B+BPF_ABS, SKF_AD_OFF+SKF_AD_IFINDEX),
BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, ifindex, 0, 5),
/* destination address: is ... */
BPF_STMT(BPF_LD+BPF_W+BPF_ABS, offsetof(struct iphdr, daddr)),
/* broadcast, as received from the local network */
@ -390,7 +396,7 @@ static void setup_interface(private_kernel_listener_t *this)
DBG1(DBG_NET, "using forecast interface %s", current->ifa_name);
this->ifindex = get_ifindex(this, current->ifa_name);
in = (struct sockaddr_in*)current->ifa_broadaddr;
attach_filter(this->pkt, in->sin_addr.s_addr);
attach_filter(this->pkt, in->sin_addr.s_addr, this->ifindex);
join_groups(this, current->ifa_addr);
host = host_create_from_sockaddr(current->ifa_broadaddr);
if (host)