net: mctp: separate cb from direct-addressing routing

Now that we have the dst->haddr populated by sendmsg (when extended
addressing is in use), we no longer need to stash the link-layer address
in the skb->cb.

Instead, only use skb->cb for incoming lladdr data.

While we're at it: remove cb->src, as was never used.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Link: https://patch.msgid.link/20250702-dev-forwarding-v5-4-1468191da8a4@codeconstruct.com.au
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/include/net/mctp.h b/include/net/mctp.h
index 6c9c5c48f59a1bf45f9c9d274a3ca2b633e96c75..b3af0690f60749a9bf9f489c7118c82cfd9d577e 100644 (file)
--- a/include/net/mctp.h
+++ b/include/net/mctp.h
@@ -183,8 +183,8 @@ struct mctp_sk_key {
 struct mctp_skb_cb {
        unsigned int    magic;
        unsigned int    net;
-       int             ifindex; /* extended/direct addressing if set */
-       mctp_eid_t      src;
+       /* fields below provide extended addressing for ingress to recvmsg() */
+       int             ifindex;
        unsigned char   halen;
        unsigned char   haddr[MAX_ADDR_LEN];
 };

diff --git a/net/mctp/route.c b/net/mctp/route.c
index 3985388a6035377c04c4e4f183c4fceca8111917..23f339b4364316817b90b4fb2952c9eac445dd24 100644 (file)
--- a/net/mctp/route.c
+++ b/net/mctp/route.c
@@ -561,35 +561,28 @@ out:
 
 static int mctp_dst_output(struct mctp_dst *dst, struct sk_buff *skb)
 {
-       struct mctp_skb_cb *cb = mctp_cb(skb);
        struct mctp_hdr *hdr = mctp_hdr(skb);
        char daddr_buf[MAX_ADDR_LEN];
        char *daddr = NULL;
        int rc;
 
        skb->protocol = htons(ETH_P_MCTP);
+       skb->pkt_type = PACKET_OUTGOING;
 
        if (skb->len > dst->mtu) {
                kfree_skb(skb);
                return -EMSGSIZE;
        }
 
-       /* If we're forwarding, we don't want to use the input path's cb,
-        * as it holds the *source* hardware addressing information.
-        *
-        * We will have a PACKET_HOST skb from the dev, or PACKET_OUTGOING
-        * from a socket; only use cb in the latter case.
-        */
-       if (skb->pkt_type == PACKET_OUTGOING && cb->ifindex) {
-               /* direct route; use the hwaddr we stashed in sendmsg */
-               if (cb->halen != skb->dev->addr_len) {
+       /* direct route; use the hwaddr we stashed in sendmsg */
+       if (dst->halen) {
+               if (dst->halen != skb->dev->addr_len) {
                        /* sanity check, sendmsg should have already caught this */
                        kfree_skb(skb);
                        return -EMSGSIZE;
                }
-               daddr = cb->haddr;
+               daddr = dst->haddr;
        } else {
-               skb->pkt_type = PACKET_OUTGOING;
                /* If lookup fails let the device handle daddr==NULL */
                if (mctp_neigh_lookup(dst->dev, hdr->dest, daddr_buf) == 0)
                        daddr = daddr_buf;
@@ -1009,7 +1002,6 @@ int mctp_local_output(struct sock *sk, struct mctp_dst *dst,
                      struct sk_buff *skb, mctp_eid_t daddr, u8 req_tag)
 {
        struct mctp_sock *msk = container_of(sk, struct mctp_sock, sk);
-       struct mctp_skb_cb *cb = mctp_cb(skb);
        struct mctp_sk_key *key;
        struct mctp_hdr *hdr;
        unsigned long flags;
@@ -1064,9 +1056,6 @@ int mctp_local_output(struct sock *sk, struct mctp_dst *dst,
        skb_reset_network_header(skb);
        skb->dev = dst->dev->dev;
 
-       /* cb->net will have been set on initial ingress */
-       cb->src = saddr;
-
        /* set up common header fields */
        hdr = mctp_hdr(skb);
        hdr->ver = 1;