[tipc-discussion] [PATCHv3 net 1/3] tipc: add tipc_bearer_min_mtu to calculate min mtu

[Xin Long]

As different media may requires different min mtu, and even the
same media with different net family requires different min mtu,
add tipc_bearer_min_mtu() to calculate min mtu accordingly.

This API will be used to check the new mtu when doing the link
mtu negotiation in the next patch.

Signed-off-by: Xin Long <lucien....@gmail.com>
Acked-by: Jon Maloy <jma...@redhat.com>
---
v2:
- use bearer_get() to avoid the open code.
v3:
- move the change history under ---, as Tung suggested.
---
 net/tipc/bearer.c    | 13 +++++++++++++
 net/tipc/bearer.h    |  3 +++
 net/tipc/udp_media.c |  5 +++--
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/net/tipc/bearer.c b/net/tipc/bearer.c
index 35cac7733fd3..0e9a29e1536b 100644
--- a/net/tipc/bearer.c
+++ b/net/tipc/bearer.c
@@ -541,6 +541,19 @@ int tipc_bearer_mtu(struct net *net, u32 bearer_id)
        return mtu;
 }
 
+int tipc_bearer_min_mtu(struct net *net, u32 bearer_id)
+{
+       int mtu = TIPC_MIN_BEARER_MTU;
+       struct tipc_bearer *b;
+
+       rcu_read_lock();
+       b = bearer_get(net, bearer_id);
+       if (b)
+               mtu += b->encap_hlen;
+       rcu_read_unlock();
+       return mtu;
+}
+
 /* tipc_bearer_xmit_skb - sends buffer to destination over bearer
  */
 void tipc_bearer_xmit_skb(struct net *net, u32 bearer_id,
diff --git a/net/tipc/bearer.h b/net/tipc/bearer.h
index 490ad6e5f7a3..bd0cc5c287ef 100644
--- a/net/tipc/bearer.h
+++ b/net/tipc/bearer.h
@@ -146,6 +146,7 @@ struct tipc_media {
  * @identity: array index of this bearer within TIPC bearer array
  * @disc: ptr to link setup request
  * @net_plane: network plane ('A' through 'H') currently associated with bearer
+ * @encap_hlen: encap headers length
  * @up: bearer up flag (bit 0)
  * @refcnt: tipc_bearer reference counter
  *
@@ -170,6 +171,7 @@ struct tipc_bearer {
        u32 identity;
        struct tipc_discoverer *disc;
        char net_plane;
+       u16 encap_hlen;
        unsigned long up;
        refcount_t refcnt;
 };
@@ -232,6 +234,7 @@ int tipc_bearer_setup(void);
 void tipc_bearer_cleanup(void);
 void tipc_bearer_stop(struct net *net);
 int tipc_bearer_mtu(struct net *net, u32 bearer_id);
+int tipc_bearer_min_mtu(struct net *net, u32 bearer_id);
 bool tipc_bearer_bcast_support(struct net *net, u32 bearer_id);
 void tipc_bearer_xmit_skb(struct net *net, u32 bearer_id,
                          struct sk_buff *skb,
diff --git a/net/tipc/udp_media.c b/net/tipc/udp_media.c
index c2bb818704c8..0a85244fd618 100644
--- a/net/tipc/udp_media.c
+++ b/net/tipc/udp_media.c
@@ -738,8 +738,8 @@ static int tipc_udp_enable(struct net *net, struct 
tipc_bearer *b,
                        udp_conf.local_ip.s_addr = local.ipv4.s_addr;
                udp_conf.use_udp_checksums = false;
                ub->ifindex = dev->ifindex;
-               if (tipc_mtu_bad(dev, sizeof(struct iphdr) +
-                                     sizeof(struct udphdr))) {
+               b->encap_hlen = sizeof(struct iphdr) + sizeof(struct udphdr);
+               if (tipc_mtu_bad(dev, b->encap_hlen)) {
                        err = -EINVAL;
                        goto err;
                }
@@ -760,6 +760,7 @@ static int tipc_udp_enable(struct net *net, struct 
tipc_bearer *b,
                else
                        udp_conf.local_ip6 = local.ipv6;
                ub->ifindex = dev->ifindex;
+               b->encap_hlen = sizeof(struct ipv6hdr) + sizeof(struct udphdr);
                b->mtu = 1280;
 #endif
        } else {
-- 
2.39.1



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