3 files changed, 37 insertions, 0 deletions

diff --git a/include/linux/llc.h b/include/linux/llc.h
index 7733585603f1..ad7074ba81af 100644
--- a/include/linux/llc.h
+++ b/include/linux/llc.h
@@ -36,6 +36,7 @@ enum llc_sockopts {
         LLC_OPT_BUSY_TMR_EXP,   /* busy state expire time (secs). */
         LLC_OPT_TX_WIN,         /* tx window size. */
         LLC_OPT_RX_WIN,         /* rx window size. */
+        LLC_OPT_PKTINFO,        /* ancillary packet information. */
         LLC_OPT_MAX
 };
 
@@ -70,6 +71,12 @@ enum llc_sockopts {
 #define LLC_SAP_RM      0xD4            /* Resource Management          */
 #define LLC_SAP_GLOBAL  0xFF            /* Global SAP.                  */
 
+struct llc_pktinfo {
+        int lpi_ifindex;
+        unsigned char lpi_sap;
+        unsigned char lpi_mac[IFHWADDRLEN];
+};
+
 #ifdef __KERNEL__
 #define LLC_SAP_DYN_START       0xC0
 #define LLC_SAP_DYN_STOP        0xDE
diff --git a/include/net/llc_conn.h b/include/net/llc_conn.h
index e2374e34989f..fe982fd94c4a 100644
--- a/include/net/llc_conn.h
+++ b/include/net/llc_conn.h
@@ -76,6 +76,7 @@ struct llc_sock {
         u32                 rx_pdu_hdr;    /* used for saving header of last pdu
                                               received and caused sending FRMR.
                                               Used for resending FRMR */
+        u32                 cmsg_flags;
 };
 
 static inline struct llc_sock *llc_sk(const struct sock *sk)
diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
index 3a66546cad06..ac691fe08076 100644
--- a/net/llc/af_llc.c
+++ b/net/llc/af_llc.c
@@ -47,6 +47,10 @@ static int llc_ui_wait_for_busy_core(struct sock *sk, long timeout);
 #define dprintk(args...)
 #endif
 
+/* Maybe we'll add some more in the future. */
+#define LLC_CMSG_PKTINFO        1
+
+
 /**
  *      llc_ui_next_link_no - return the next unused link number for a sap
  *      @sap: Address of sap to get link number from.
@@ -591,6 +595,20 @@ static int llc_wait_data(struct sock *sk, long timeo)
         return rc;
 }
 
+static void llc_cmsg_rcv(struct msghdr *msg, struct sk_buff *skb)
+{
+        struct llc_sock *llc = llc_sk(skb->sk);
+
+        if (llc->cmsg_flags & LLC_CMSG_PKTINFO) {
+                struct llc_pktinfo info;
+
+                info.lpi_ifindex = llc_sk(skb->sk)->dev->ifindex;
+                llc_pdu_decode_dsap(skb, &info.lpi_sap);
+                llc_pdu_decode_da(skb, info.lpi_mac);
+                put_cmsg(msg, SOL_LLC, LLC_OPT_PKTINFO, sizeof(info), &info);
+        }
+}
+
 /**
  *      llc_ui_accept - accept a new incoming connection.
  *      @sock: Socket which connections arrive on.
@@ -812,6 +830,8 @@ copy_uaddr:
                 memcpy(uaddr, llc_ui_skb_cb(skb), sizeof(*uaddr));
                 msg->msg_namelen = sizeof(*uaddr);
         }
+        if (llc_sk(sk)->cmsg_flags)
+                llc_cmsg_rcv(msg, skb);
         goto out;
 }
 
@@ -1030,6 +1050,12 @@ static int llc_ui_setsockopt(struct socket *sock, int level, int optname,
                         goto out;
                 llc->rw = opt;
                 break;
+        case LLC_OPT_PKTINFO:
+                if (opt)
+                        llc->cmsg_flags |= LLC_CMSG_PKTINFO;
+                else
+                        llc->cmsg_flags &= ~LLC_CMSG_PKTINFO;
+                break;
         default:
                 rc = -ENOPROTOOPT;
                 goto out;
@@ -1083,6 +1109,9 @@ static int llc_ui_getsockopt(struct socket *sock, int level, int optname,
                 val = llc->k;                           break;
         case LLC_OPT_RX_WIN:
                 val = llc->rw;                          break;
+        case LLC_OPT_PKTINFO:
+                val = (llc->cmsg_flags & LLC_CMSG_PKTINFO) != 0;
+                break;
         default:
                 rc = -ENOPROTOOPT;
                 goto out;