--- name: "ibv_post_send" section: "3" platform: "linux" package: "rdma-core" version: "65.0-1" release: "Arch Linux 2026-11-01" platforms: ["linux", "freebsd"] url: "https://new.carta.tech/ibv_post_send" --- # ibv\_post\_send(3) post a list of work requests (WRs) to a send queue ## NAME ibv\_post\_send - post a list of work requests (WRs) to a send queue ## SYNOPSIS ``` #include int ibv_post_send(struct ibv_qp *qp, struct ibv_send_wr *wr, struct ibv_send_wr **bad_wr); ``` ## DESCRIPTION **ibv\_post\_send()** posts the linked list of work requests (WRs) starting with *wr* to the send queue of the queue pair *qp.* It stops processing WRs from this list at the first failure (that can be detected immediately while requests are being posted), and returns this failing WR through *bad\_wr.* The argument *wr* is an ibv\_send\_wr struct, as defined in \. ``` struct ibv_send_wr { uint64_t wr_id; /* User defined WR ID */ struct ibv_send_wr *next; /* Pointer to next WR in list, NULL if last WR */ struct ibv_sge *sg_list; /* Pointer to the s/g array */ int num_sge; /* Size of the s/g array */ enum ibv_wr_opcode opcode; /* Operation type */ unsigned int send_flags; /* Flags of the WR properties */ union { __be32 imm_data; /* Immediate data (in network byte order) */ uint32_t invalidate_rkey; /* Remote rkey to invalidate */ }; union { struct { uint64_t remote_addr; /* Start address of remote memory buffer */ uint32_t rkey; /* Key of the remote Memory Region */ } rdma; struct { uint64_t remote_addr; /* Start address of remote memory buffer */ uint64_t compare_add; /* Compare operand */ uint64_t swap; /* Swap operand */ uint32_t rkey; /* Key of the remote Memory Region */ } atomic; struct { struct ibv_ah *ah; /* Address handle (AH) for the remote node address */ uint32_t remote_qpn; /* QP number of the destination QP */ uint32_t remote_qkey; /* Q_Key number of the destination QP */ } ud; } wr; union { struct { uint32_t remote_srqn; /* Number of the remote SRQ */ } xrc; } qp_type; union { struct { struct ibv_mw *mw; /* Memory window (MW) of type 2 to bind */ uint32_t rkey; /* The desired new rkey of the MW */ struct ibv_mw_bind_info bind_info; /* MW additional bind information */ } bind_mw; struct { void *hdr; /* Pointer address of inline header */ uint16_t hdr_sz; /* Inline header size */ uint16_t mss; /* Maximum segment size for each TSO fragment */ } tso; }; }; ``` ``` struct ibv_mw_bind_info { struct ibv_mr *mr; /* The Memory region (MR) to bind the MW to */ uint64_t addr; /* The address the MW should start at */ uint64_t length; /* The length (in bytes) the MW should span */ unsigned int mw_access_flags; /* Access flags to the MW. Use ibv_access_flags */ }; ``` ``` struct ibv_sge { uint64_t addr; /* Start address of the local memory buffer or number of bytes from the start of the MR for MRs which are IBV_ACCESS_ZERO_BASED */ uint32_t length; /* Length of the buffer */ uint32_t lkey; /* Key of the local Memory Region */ }; ``` Each QP Transport Service Type supports a specific set of opcodes, as shown in the following table: ``` OPCODE | IBV_QPT_UD | IBV_QPT_UC | IBV_QPT_RC | IBV_QPT_XRC_SEND | IBV_QPT_RAW_PACKET ----------------------------+------------+------------+------------+------------------+-------------------- IBV_WR_SEND | X | X | X | X | X IBV_WR_SEND_WITH_IMM | X | X | X | X | IBV_WR_RDMA_WRITE | | X | X | X | IBV_WR_RDMA_WRITE_WITH_IMM | | X | X | X | IBV_WR_RDMA_READ | | | X | X | IBV_WR_ATOMIC_CMP_AND_SWP | | | X | X | IBV_WR_ATOMIC_FETCH_AND_ADD | | | X | X | IBV_WR_LOCAL_INV | | X | X | X | IBV_WR_BIND_MW | | X | X | X | IBV_WR_SEND_WITH_INV | | X | X | X | IBV_WR_TSO | X | | | | X ``` The attribute send\_flags describes the properties of the WR. It is either 0 or the bitwise OR of one or more of the following flags: - **IBV\_SEND\_FENCE Set the fence indicator. Valid only for QPs with Transport Service Type IBV\_QPT\_RC** - **IBV\_SEND\_SIGNALED Set the completion notification indicator. Relevant only if QP was created with sq\_sig\_all=0** - **IBV\_SEND\_SOLICITED Set the solicited event indicator. Valid only for Send and RDMA Write with immediate** - **IBV\_SEND\_INLINE Send data in given gather list as inline data** in a send WQE. Valid only for Send and RDMA Write. The L\_Key will not be checked. - **IBV\_SEND\_IP\_CSUM Offload the IPv4 and TCP/UDP checksum calculation.** Valid only when **device\_cap\_flags** in device\_attr indicates current QP is supported by checksum offload. ## RETURN VALUE **ibv\_post\_send()** returns 0 on success, or the value of errno on failure (which indicates the failure reason). ## NOTES The user should not alter or destroy AHs associated with WRs until request is fully executed and a work completion has been retrieved from the corresponding completion queue (CQ) to avoid unexpected behavior. The buffers used by a WR can only be safely reused after WR the request is fully executed and a work completion has been retrieved from the corresponding completion queue (CQ). However, if the IBV\_SEND\_INLINE flag was set, the buffer can be reused immediately after the call returns. IBV\_WR\_DRIVER1 is an opcode that should be used to issue a specific driver operation. ## SEE ALSO [**ibv\_create\_qp**(3)](/ibv_create_qp/3.md), [**ibv\_create\_ah**(3)](/ibv_create_ah/3.md), [**ibv\_post\_recv**(3)](/ibv_post_recv/3.md), [**ibv\_post\_srq\_recv**(3)](/ibv_post_srq_recv/3.md), [**ibv\_poll\_cq**(3)](/ibv_poll_cq/3.md) ## AUTHORS - Dotan Barak \ - Majd Dibbiny \ - Yishai Hadas \