In case UDP traffic is redirected to a local UDP socket, the originally addressed destination address/port cannot be recovered with the in-kernel tproxy. This patch adds an IP_RECVORIGDSTADDR sockopt that enables a IP_ORIGDSTADDR ancillary message in recvmsg(). This ancillary message contains the original destination address/port of the packet being received. Please apply. Signed-off-by: Balazs Scheidler <bazsi@balabit.hu> --- include/linux/in.h | 4 ++++ net/ipv4/ip_sockglue.c | 40 +++++++++++++++++++++++++++++++++++++++- 2 files changed, 43 insertions(+), 1 deletions(-) diff --git a/include/linux/in.h b/include/linux/in.h index db458be..d60122a 100644 --- a/include/linux/in.h +++ b/include/linux/in.h @@ -80,6 +80,10 @@ struct in_addr { /* BSD compatibility */ #define IP_RECVRETOPTS IP_RETOPTS +/* TProxy original addresses */ +#define IP_ORIGDSTADDR 20 +#define IP_RECVORIGDSTADDR IP_ORIGDSTADDR + /* IP_MTU_DISCOVER values */ #define IP_PMTUDISC_DONT 0 /* Never send DF frames */ #define IP_PMTUDISC_WANT 1 /* Use per route hints */ diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c index 465abf0..1e70488 100644 --- a/net/ipv4/ip_sockglue.c +++ b/net/ipv4/ip_sockglue.c @@ -48,6 +48,7 @@ #define IP_CMSG_RECVOPTS 8 #define IP_CMSG_RETOPTS 16 #define IP_CMSG_PASSSEC 32 +#define IP_CMSG_ORIGDSTADDR 64 /* * SOL_IP control messages. @@ -126,6 +127,27 @@ static void ip_cmsg_recv_security(struct msghdr *msg, struct sk_buff *skb) security_release_secctx(secdata, seclen); } +void ip_cmsg_recv_dstaddr(struct msghdr *msg, struct sk_buff *skb) +{ + struct sockaddr_in sin; + struct iphdr *iph = ip_hdr(skb); + u16 *ports = (u16 *) skb_transport_header(skb); + + if (skb_transport_offset(skb) + 4 > skb->len) + return; + + /* All current transport protocols have the port numbers in the + * first four bytes of the transport header and this function is + * written with this assumption in mind. + */ + + sin.sin_family = AF_INET; + sin.sin_addr.s_addr = iph->daddr; + sin.sin_port = ports[1]; + memset(sin.sin_zero, 0, sizeof(sin.sin_zero)); + + put_cmsg(msg, SOL_IP, IP_ORIGDSTADDR, sizeof(sin), &sin); +} void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb) { @@ -160,6 +182,12 @@ void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb) if (flags & 1) ip_cmsg_recv_security(msg, skb); + + if ((flags>>=1) == 0) + return; + if (flags & 1) + ip_cmsg_recv_dstaddr(msg, skb); + } int ip_cmsg_send(struct net *net, struct msghdr *msg, struct ipcm_cookie *ipc) @@ -421,7 +449,8 @@ static int do_ip_setsockopt(struct sock *sk, int level, (1<<IP_ROUTER_ALERT) | (1<<IP_FREEBIND) | (1<<IP_PASSSEC) | (1<<IP_TRANSPARENT))) || optname == IP_MULTICAST_TTL || - optname == IP_MULTICAST_LOOP) { + optname == IP_MULTICAST_LOOP || + optname == IP_RECVORIGDSTADDR) { if (optlen >= sizeof(int)) { if (get_user(val, (int __user *) optval)) return -EFAULT; @@ -509,6 +538,12 @@ static int do_ip_setsockopt(struct sock *sk, int level, else inet->cmsg_flags &= ~IP_CMSG_PASSSEC; break; + case IP_RECVORIGDSTADDR: + if (val) + inet->cmsg_flags |= IP_CMSG_ORIGDSTADDR; + else + inet->cmsg_flags &= ~IP_CMSG_ORIGDSTADDR; + break; case IP_TOS: /* This sets both TOS and Precedence */ if (sk->sk_type == SOCK_STREAM) { val &= ~3; @@ -1022,6 +1057,9 @@ static int do_ip_getsockopt(struct sock *sk, int level, int optname, case IP_PASSSEC: val = (inet->cmsg_flags & IP_CMSG_PASSSEC) != 0; break; + case IP_RECVORIGDSTADDR: + val = (inet->cmsg_flags & IP_CMSG_ORIGDSTADDR) != 0; + break; case IP_TOS: val = inet->tos; break; -- 1.5.4.3 -- Bazsi